What "other performance aspects" are you concerned about?
About the only performance advantages I can see in a bracket is the claimed 2-3 mph increase in WOT speed in flat water, which comes at the expense of ride and low speed planing capability. You gain WOT speed due to the CG shift caused by moving motor ~30" aft, which raises the bow, reducing wetted surface and drag. My experience is that when you apply the necessary band aids (AV plate fin & 4B prop) to regain low speed planing capability and good ride, you'll lose most of the WOT speed you gained with the bracket! So all the bracket really buys you is a bit more room in the boat AND the safety of a solid transom (which IS a significant improvement if you run offshore very much!)
What you're really asking about is how much should you shift the CG, if any? I would never claim to be smarter than Carl Moesly who designed these boats after decades of boat building, flying and racing experience, so I'd try to keep the CG as close to the design point as possible!
Here's what I'd recommend to calculate an approximate distance to move stuff:
1. Assume the as-designed CG was at the center of the fuel tank. (As a veteran pilot of military transports, Moesly knew how important it was to not change trim as you burn off fuel!)
2. Assume the design motor weight was 300 lbs, on transom, with a single battery at stbd chine just ahead of transom. The design "Motor moment" is (300 lbs) X (distance from transom to center of fuel tank).
3. Use weight of new motor (not the advertized "dry" weight, but "wet" weight including oil & gear lube @ 7.3 lbs/gal, plus weight of the cowling) plus the bracket setback dimension to calculate a new "Motor Moment".
4. The increase of the motor moment, in ft-lbs, is what you'll want to offset by moving batteries, fuel tank, console, etc. so by knowing what all that stuff weighs, you should be able to figure out how far you'll have to move it.
BTW, when looking at these newer "light weight/large displacement" 4-stroke motors, remember that they got most of the weight savings by just removing iron cylinder sleeves! That means that if, for whatever reason (clogged filter, stuck anti-siphon valve, air leak, fuel hose kink), you ever starve the engine for fuel that leans out & overheats a piston and scuffs a cylinder, all it'll take to fix it is a new block! The days of a simple bore & hone plus piston replacement are history for those motors. That's why the modern DI 2-strokes, which achieve even lighter weight, quiet smokeless operation, and low fuel burn without that compromise, are worth a hard look IMHO!
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