I agree that a four-yard belted plaid is sufficient. I am not exactly slim and four yards is very adequate for me - and I have a three-yard plaid that works, too - just don't overlap the pleats as much when you don it. When I first got into Highland reenacting, I wore a six yard plaid for a year or two and it was both heavy and occasionally rubbed up a blister or twa on my waist because I had to cinch the waist-belt so tight to keep the heavy plaid from slipping down.

I think that making hose from the surplus two yards is an excellent idea! Be sure to cut the hose out on the bias and with the twill lines vertical. With good pattern layout, you should be able to get three pair of hose (minimum) out of two yards of double-width tartan. Once you get a pattern worked out that fits, it doesn't take long to make a pair of hose. I can make a pair in about two hours from layout to last stitch. And you can use the same pattern to make as many pairs as you please. Just remember to make the foot part a little big - slightly wider and longer than necessary (remember, feet swell up and wool shrinks, and too-small hose - especially in the toe area - are as uncomfortable as it gets) and allow enough room in the ankle to get your foot through. The part that encloses your calves should be tight.

Good luck with it!