It seems that for the most part, I prefer forearms to be a little longer than you guys. Here's a list of a few of mine, measuring lop and forearm length from the trigger...
Jacob Kuntz - LOP 13 3/4" forearm 14 1/4" bbl 44" (documentary copy)
A. Verner - LOP 13 1/2" forearm 13 3/4" bbl 48" (documentary copy)
Jaeger - LOP 13 7/8" forearm 10 1/4" bbl 31" (my own design)
P. Berry - LOP 14" forearm 12 1/2" bbl 42" (Berry influenced, but not a copy)
Mark Silver Virginia - LOP 14" forearm 13 1/4" bbl 42" (Chambers' parts set)
PA Fowler - LOP 13 3/4" forearm 16 1/8" bbl 46" (Chambers' parts set
Ketland fowler - LOP 13" forearm 19 5/8" bbl 47 3/4" (original and half-stocked)
Except for the last, the Ketland fowler, all these guns look quite in proportion. I think that a shorter forearm would make a big difference in the architecture of the thing. In the end, I suppose it's a matter of personal preference. But one should study originals for the answer to this question.