Caerphilly was traditionally made in 10 diameter cheeses of 8 lbs (forget where I got that, it's just in my notes). It was also pressed in the 7-8 PSI range. I'm only able to get to just over 2 psi, so I'm already quite light. Anyway, caerphilly would be sent to market after 2 weeks, so I don't think you'll need any more time to age it out. The moisture content is more determined by the make process (floc multiplier; the size you cut the curd, temperature you cook it at, how vigorous you stir, and how long you cook and stirr, are the variables that are typically targeted to adjust moisture content. Pressing weights is more about knit and getting rid of internal spaces - or ensuring there are some, as with blues).
Anyway, look forward to seeing your make.
Here is the 1907 newspaper article where found the protocol I adapted to make this cheese , along with some notes of mine at the end:
Marlborough Express, Volume XL, Issue 15, 18 January, 1907, page 4
This is one of those makes of cheese for which there is at the present time a steadily growing demand. So large, indeed, has the consumption of this cheese become (writes C.W. Walker-Tisdale in the Farmer and Stockbreeder) that we know of one firm of cheese merchants which is having Caerphilly specially manufactured in New Zealand, Holland, and Denmark, and sent to it in order to make the supply anything like equal to the demand. It appears to me that the prospects for this cheese are better than for almost any other variety, and considering the number of Cheddar makers who are turning their attention to Caerphilly makes, the production of Cheddar cheese is likely to suffer in consequence. The advantages of producing Caerphilly cheese as compared with Cheddar are: 1 Greater weight of cheese is obtained, as it is sold fresh when in a moist condition. 2. Being sold at the end of a fortnight after making, very little storage room is required. 3. The sale being effected so soon after making, money is quickly returned for the milk, which is not the case where Cheddar cheese is made, as this does not fully ripen and become ready for market in a less period than three months. To manufacture this cheese new milk is taken, regulated to a temperature of 86 deg. Fahr., and rennetted in the proportion of one drachm of rennet to three gallons of milk (rennet being first diluted with cold water.) In the course of about an hour the curd will be firm enough to manipulate, which can be tested by seeing if it breaks clean over the finger. It may then be cut by using American knives’ (vertical and horizontal), and reduced to small cubes of about 1in in size. When all the curd is reduced to this size the temperature of the whole contents of the vat should be raised to 86deg. Fahr., as by this time it will probably have fallen several degrees, so should be raised to the same temperature as that at which it was rennetted. The curd must now be stirred by hand for about an hour, or until it becomes slightly firm in nature. Some makers stir the curd for thirty minutes, allow it to pitch or settle in the bottom of the van (sic; I assume vat) for ten minutes, when it will be time to draw off the whey. The whey is now drawn off, and the curd is placed in coarse cloths and placed on a table to drain. To help the expulsion of whey the cloths are tightened now and again by taking three corners and using the fourth as a binder. This drainage is allowed to go on for about an hour, during which time the cloths will have been tightened about five times. This tightening to expel the whey must not be excessive, or the curd will get too dry. The curd is now broken by squeezing it in the hand and out between the fingers, almost as a potato-masher works. It is next placed in the tin moulds, which are lined with cloths to receive, and the curd pressed in with the hands. The curd in the moulds is left for two hours before being put to press, during which time only small weights are put on the followers to keep the curd together. The curd in the moulds may now be turned and put to press under just a small amount of pressure – say, 5cwt or 6cwt overnight. In twelve hours’ time (next day) the cheeses are taken out, rubbed with salt, turned, and replaced in the mould with a fresh cloth, and put under a pressure of about 10cwt. Twelve hours later this process is repeated, the total amount of salt used being half an ounce to each pound of cheese. On the third morning from making the cheese may be taken out of the press and removed to the curing-room, which, if the cheese is to be ready for sale in two weeks’ time, should be at a temuerature (sic) of 65deg. to 20deg. (sic : 70?) Fahr. If not required to be ripe so soon it must be kept at a lower temperature. In some cases makers prefer to salt their cheese by brining them instead of rubbing with dry salt. This may be done by having the cheeses partly immersed in brine for a couple of days or so, being careful to turn them frequently. The common size of the Caerphilly cheese is 6lb, but they are made in sizes from 5lb to 10lb each. In the case only of the larger cheeses the pressure may be increased to 15cwt instead of 10cwt for full pressure.
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For noting: cwt is a hundredweight, or “centum weight”. In the UK (and here in New Zealand), 1 cwt = 112 pounds, while in the US it equals 100 lbs.
And a drachm is 1/8th of a fluid ounce according to "thefreedictionary.com"
I've also found reference to the traditional sizes being 10 inches in diameter and 8lbs. Assuming 10 inch diameters then 5cwt would produce roughly 7.13 psi, 6 cwt would give 8.56 psi, 10cwt = 14.27 psi, and 15cwt = 21.40 psi