How much of a difference would going from 34" center to center to 35" make on a high 90 mph boat?
Reson being, most exhaust needs at least. 34.5" to fit side by side, esp on a tall deck or high port heads. My current boat is 34" and the headers are 1/8" apart. New boat I'm starting on I wouldn't mind a little more room or opportunity to use tall deck blocks, or big brodix heads. Not sure they will be necccesary, but also nice to not be limited on exhaust choices.

Not much difference... Look at it this way, they dont gain all the much (under 100mph) from a full stagger (18") to a semi (24") stagger setup. Back in the day Fountain would even go with a 33.5 CL and nest the headers... but ended up going away from it, cause it was not worth the pain. I think you answered your own question as in... being able to have some room to work... Besides ever dock a full stagger??? LOL

I`m almost 36" and its nice to fit whatever header I want.

WOW...baby got back... lol

Several times, full stagger, 900's,6's with 5 blades spinning in. I don't actually find it that hard.
Rough rider, and a Maximus.

I'm trying to get close to 100 with 800's gotta weigh out room to work for efficiency lol

I`d need 1650s top get to a 100 lol

Nah 1200's should do it! Lol