The way he explained it for the XS anyway, we never got into the XB other than he did say they require more setback than the XS in the neighbor hood of 14 he said were the Xs at 10.5 should be all i would need or less. I know Ziemer is at like 8.5 or 9.5 and others also. Todd is at 12 were I was. BTW before i explain how he said it i do notice I need less trim to get a spray at over 80 equal to the hight of the top of the cowl.
The way he explained it was the down force created when you accelerate. If the motor is closer to the transom the fulcrum point there for is more forward on the hull and the down forces on the pad are less when accelerating. Hence requiring less trim at even with the pad.
So now think of it the other way. More setback. The farther back the motor the farther back the fulcrum point. This also will make your bow rise more as the weight has been distributed farther back. As you take off the stern will squat more on an XS. This in turn barries your gearcase more and will require more trim to get the pad and gearcase running up were it belongs.
Every time Ive talk to Darris about this sorta stuff he always referse for simplicaty sake the teeter toter effect. As the motor spins the prop the back end digs a hole and the bow will rise. The closer to the transom the less of a hole having more weight forward.:banghead
When Darris refered to the XB he said a fishin load XB requires more setback. If i always had a load then then 12 would probably be better. Im usually by my self or only have one passanger now and then exept when schools out and the kids can come with me on the week days. A passanger in the back seat is going to move my fulcrum point way back. Having more setback would help in this situation. Less setback for skiing because the tall pylon is trying to pull the stern down to the point were the bow rises like its going over backward. If the motor had less in this case I would be moving the fulcum forward and the stern would be getting a little help by less setback.
On the GS the bow is very very light. i cant even walk on my deck. i crawed once on there and never again. The creeks and grows from it being so thin detured me from ever tempting this again. The bow is just an empty void. On the XB you have storage compartments a deck strong enough to walk on and a troller that must weigh 10lbs at least right at the tip of the bow. Allisons being weight sensitive as you all are aware must contribute to what he says for needing more setback than a xs on a XB hulls created equel. Take full live wells and add some rods and tackel into the equation and there would be quite a bit more down force at the bow than the XS when taking off and in 800ft loaded requiring a little extra setback. This does make sence to me. Now for practical testes im sure everyone who has tried differant setups will have differant results.
Personaly I need one or two more good days on the lake without any one there to make a real determination if i will keep my 10.5 over the 12 I had her at. But the one day on a busy lake I did have after some getting used to the differants in trim was noticable. I think I still need to move a bag around a bit yet to dial her in when Im alone. Full fuel and three passangers might be a diferant story?