Apologies if this has been covered somewhere before. I've been reading TTSM ch. 4 over and over, and I can't quite seem to find a clear authoritative answer to what seems to me a basic question. Exactly what are the numerical dimensions of the transverse frames? Piecing together various internet sources and putting rulers to the drawings, I *think* I'm coming up with a channel of 10" x 4" x 0.5", at least admidship. Is that correct? At what point do the dimensions start to decrease, and how much smaller does it get before the construction changes to angle/reverse frame?