So I was at Melissa and Adam's on Friday and was checking out one of their shields because I plan on using one next year. It's a round shield, 28" diameter. Melissa pointed out that the shield was to large for me to use because it extended past my shoulders. I was

But then I decided to do some math. I measured my chin to the the floor while on my knees (Insert joke here) and the width of my shoulders. My results were 38" from chin to the floor and 22" from shoulder to shoulder. That would mean that the largest shiel I could legally use would have a surface area of 836 inches. The round shield would only have a surface area of 617". That's about 25% smaller than a max size shield would be for me.
So I guess where I'm going with this is that I want to use the round shield. And I feel I or anybody else in this situation should be allowed to because it's smaller than what a shield built at maximum specs would be. I know this seems complicated but...
Measure a PC's width at their shoulders and from their chin to the floor. Figure out what the max size shield they can use is and put it on their character sheet.
Shields will have the surface area they cover on the shield, on a tag. If it's surface area is larger than your max shield size than you can't use it.
Example:
Bob notices his friend Tom has dropped in battle and wants to use Tom's shield. After getting permission from Tom to use the phys rep Bob looks at the back of the shield to check size. The max shield size Bob can use is 660 inches. The tag on the back of the shield says it's surface area is 700 inches. Bob can't legally use the shield in combat so places the shield back down.
Thoughts?