Outboard generator shelf w/ 6bta's

[my other east]

Hello Faithful.
I'm looking for some advice on the length of a shelf i want to build prior to the engines (gas to diesel conversion) going back in.
It's not so much the length, but how much clearance i should leave for the 5" Tony Athens exhaust risers running aft thru the bulkhead.
6", 8", 10" inches?
Any help would be deeply appreciated, i'd hate to have to hack them after they are in.

[bob lico]

Attached to hull then leave 2" next to outboard stringer.then lay up to main bulkhead and extend 30" the 3/4" stock should actually fit in the groove that the reverse chine makes on the inside of the hull .make level and you will need a three inch or so upright piece x 30" for this gen support to rest on.

[bob lico]

[my other east]

Thanks Bob, just the info i was looking for.
This site is awesome..........