My 2 cents...I once took a flashlight and looked up my exhaust from the transom to see what was in there. I saw a series of 'baffles' that alternated, 1 from the bottom and 1 from the top- so on all the way as far as I could see. Now this is on a 1990 Mariah with the 351. I too have the 45 degree angled pipe going under the rear floor. And after reading this, noticed one of my exhaust hoses looks like it could be getting hot- we also do a lot of idle speed cruising- miles at a time. I have been thinking about doing the stainless pipe section in place of the hoses you mentioned.