The nice thing about early transitional is you can start by doing arming garments, then mail. The plate needs to be worn over the mail, so the plate portion is irrelevant for a while, as you'll need measurements *over* the mail anyway. Once you have your time frame narrowed down, focus on the garments first, then mail.
Also, you can get Osprey books off Amazon. I got 10 or so of them from there.
Most chausses I've seen are like a long stocking. I need to trim mine around the feet, but they are otherwise complete. I have some "mail time" set aside this weekend to work on that and my hauberk tailoring. In testing at home - no actual long-term wearing yet - I found it easiest to put on the chausses, tie the feet/lower up out of the way, put the shoes on, then let the mail back down. It would be tied down after.
I sent Ulrich a few messages about it on FB, but I have a plan that essentially involves using some black leather trim on the inside of the chausses to have some quick and dirty, easy to tie on chausses w/feet. I'll post pics next week if I get at least one foot done this weekend.