Strathmore's medium weight tartan is great. The only caveat for your particular situation is the one I mentioned about medium weight tartan and box pleated kilts.

As all y'all no doubt are aware, different mills kind of "specialize" - Lochcarron has the hugest selection of 16 oz stock tartan, Dalgliesh has the hugest selection of dance tartans, HoE is known for their medium weight tartan and Irish County tartans, etc. etc. It helps them each keep a corner on part of the market.