Most of my squishies go at .44. The fat 8ths do. The blocks go at .44 if they're pretty flat. I use the sticky Press 'n Seal, but sometimes there are lumps from seam junctions that just make the envelope too thick. Our postmaster (who's my next-door-neighbor) uses the little template that you slide the envelope through, and if it hangs up then he recommends adding the extra .20. It's all based on the weight first (and they all weight less than an ounce) and then the thickness. I use the legal sized envelopes. So far I haven't had any returned for additional postage, and I hope the swappers on the other end don't have to pay extra, either.