You will find vac formed plastic is misshaped and thin from the process, I do however use these offcuts for inner cover strips (mainly shins as they are flexed a lot)
Before you make any cuts do a trial fit, you don't want to cut too much off, hard to get back on
Sizing of cover strips
Forearms/Biceps @15mm
Thighs 20mm
Shins Front 20mm, Rear 25mm (for velcro)
Yes you can go bigger with cover strips if you need too
A few threads on cover strips
Cover Strips threads: gazmosis, I'm Batman, sith_241, & Falciform13
ANH & ESB Cover Strip lengths and Ends by CableGuy
Scribe technique for Cover Strips by chiefbonan