This exhaust thing is driving me nuts.  Just when I think I have it, A new wrinkle.  The exhaust pipe for the generator needs to come out of the generator, and go DOWN BELOW THE FLOOR!. if you had it in you garage, it would have go down into the concrete.  So I had a choice, raise up the generator (weight up high = Bad), hard to mount a 400 lb vibrating machine up in the air.  So I chose to go down with to the lift.  It actually turned out as a really neat job.  The piece I cut out of the floor was then re-fiber glassed on the angled hull below to make a shelf.  Lift box fits right in.  Now I just need another elbow and I can connect it.  2 holes in the background are for the fuel lines going to the centre fuel tanks (I have 2 now).