Hi TimT,
To get a good knit with a cheddar type without having 200 lbs stacked upon your mould, it is important to keep the curds warm and I suspect your problem is that the curds are cooling off too much. Many of us here follow Sailor's advice of "pressing in the pot". What that means is, you keep your curds warm while cheddaring them by putting the pot in the sink in a bath of warm water, that keeps the curds warm while they sit there and you flip and stack them. Then, you mill them into small pieces in this warm pot, mix in your salt, and put the warm curds into a warmed mould (so pour warm whey over your cheese cloth and the mould, then fill them with the warm curds). Ok, now, put the mould back in the pot, and put the pot in the sink of warm water. Now put your weight on top and press for 30 minutes. If you're pressing around 1 PSI (1 pound per square inch of surface area of your follower) then the curds should knit enough for you to undress the cheese, flip, redress, and press again with a bit more weight. Keep doing this, and keep the water in the sink warm (and cover the pot, use towels, anything to keep the warm moist air in the pot with the curds). Each press and flip also increase the weight a bit (add an extra 10 lbs), until you're up over 2.5 PSI. After two hours of pressing in the pot, you can probably move the mould to a warmish room, and complete your pressing schedule (a few more flips maybe, but press until the next day with over 2.5 PSI). That doesn't take too much weight (about 35 kg on a 6.25 inch diameter mould). That should get you a decent knit.
- Jeff