When I bought my JRed 2171 last month I had the dealer switch out the JRed bar (.058) for an Oregon .050 so that my chains would be consistent among the 372XP (which came with an .050 and I have continued to replace with .050 bsrs) and my Mikita 6401. My new Stihl 361 takes 3/8 .050, but with an 18" bar (66 link chain instead of the 72 link for a 20" bar). I'm certainly not a pro logger by any means, so take my comments with as many grains of salt as you wish, but I have had really good results using the 3/8 .050 chain and just put in an order at Baileys for 16 18" loops of Woodsman Pro and 12 20" loops of the same. Any one who thinks they can save money buying rolls of chain and the necessary tools and making their own isn't very good at math.
By the way, in case you haven't already realize it, this is a great site for at least 2 things: 1. Learning about chainsaws from many genuine experts who are very generous with their time and their expertise, and, 2. Being convinced that money spent on saw and saw related gear, no matter what ithe amount might be, is money well spent.
Hugenpoet