Thanks Pat for your info. I had to sketch out your "invention" which is one of those "wish I'ld thought of that" things. You've got me thinking I might could increase the thermal air flow by adding soffit vents between each rafter on our typical brick ranch. It has end gable vents and a couple non-powered dome type vents, but it is HOT -hot in attic. Now on my barn (with 26x51 loft room ) I might employ your idea and add the additional supports in attic like in your Mom's porch. I have 2x4 scissor truss with top cord at 6-12 with 3-12 lower, and it has a nice cathedral ceiling effect. Once the metal roof goes on I expect increase in temp up there. But until I get the stairs done it ain't a problem. I suppose I could attach to the underside of top rafter cord a foil backed ridged foam (don't want to add too much weight ) and create a "plenum" about 2ft below the ridge running to the end gable vents...might need a fan in one...If this was done and I put in F/G batts on ceiling I'ld still need to vent the space between the batts and the underside of ridged foam...not sure how that would get vented perhaps I could circulate it through the shops below. I'll have to munch on this a bit. I answered my own question, I'm using 1/4x4" carriage bolts on the bander board (some call it "ledger") We get fairly high winds through here at times and I don't want the thing to blow off in a minor gust. I epoxed 1/2 anchor bolts in concrete slab for the 6x6 posts, so that is secure but I wanted the wall end to be as well...just don't trust 3/4" of nail to hold. Anyhow you've given me some avenues to ponder and I thank ya.
Have a blessed mediocre country weekend mi amigo,
rg