These are all good suggestions. Being a newbee, i have made 4 parms using 4 different recipes. All of them were small amounts of milk; 2-3 gallons. Two recipes were made with cow's milk (2%) and the remaining two recipes were made with a mixture of cow and goat milks. I too, used Ricki's recipe, once. All 4 recipes were made roughly a year ago.
By the time i chose to consume them (at a year old) i found the results to be pretty much the same. Too hard for my liking. The cantina's temp was pretty steady except for the summer months where the temperatures rose to about 60°. Humidity had fluctuated as well anywhere from 70-85%. Again, being a newbee i did not pay close attention to the numbers. The heads ended up being very small measuring at about 5" diam x 1 1/2". Compared to the starting size, this is significantly small! I'm learning. I did expect shrinkage, i just did not know how much.
I had read once in Jim Wallace's articles on parms and he said when making one, you'd be almost wasting your time using recipes with only small amounts of milk as "a larger cheese has a better surface to mass ratio for aging"...of course i read this AFTER the fact! My cheese texture was like glass!! Very dangerous to grate on a rasp or a box grater, yielding too little cheese for my poor arm. The grated cheese was not fluffy, although, the aroma and taste were good.
Next time, i would rather use 6 gallons of milk, and watch the temps and humidity closely. In my case, i allowed the cheeses to dry too long for their environment.