Its the water coming threw the tunnel on to the blades push on that water. So there is water on the inner side of the blades. So the prop turning in would push up on that water on the down stroke. On a v bottom there is no water on the inner edge of the blade. ? Lets talk more after your testing i could be wrong. I do agree more rake does give bow lift.

I have attached a thread from another site. Dale Rayzor explains the in and out thing real well.

Spinning In vs Spinning Out



For everyone that wants to know why spinning in vs spinning out causes different forces on the transom, it is all because of the angle of deadrise on the sponsons. When spinning in, there are less degrees of rotation of the blades spinning down in the water than there are degrees of rotation spinning up in the water. Therefore, the blades are spending more time in the water on the way up, than down - which equals more force generated pulling the prop down (causing bow lift). The reverse is true when spinning out, there are more degrees of rotation of the blades spinning down in the water than there are degrees of rotation spinning up in the water. Therefore, the blades are spending more time in the water on the way down, than up - which equals more force generated pushing the prop up (causing stern lift).

http://www.screamandfly.com/attachme...4&d=1392510701

I agree for a v bottom, but for a cat its different because not only the outersides of the sponsons are catching water, the water is going threw the sides of the tunnel and the prop is catching that on the inside and props are pushing up.

What if the motors are mounted far enough apart prop blade is not catching the tunnel? This has been debated for many years and different opinions. I know in talking to Johnny at TNT he has told me the same thing on many occasions. Back in the day when Tom and Bob raced the Mobil One 28 against some other 28's a few tried turning the motors in and the boats were very flighty in the rough water and all over the place.
Could not keep the nose in the water. They quickly went back to spinning out.

Testing Update 1/31/2016
 

Well after finally getting a break in the rain and family activities we were able to get some runs in.
Happy to report newly modified hull pickups worked awesome. Pick ups only 1/16" or so below bottom. Had 25lbs pressure over 90mph.
Test conditions, 75 degrees and 85 percent humidty no wind.
Same load as previous runs. 60 gallons of fuel also. This boat/motor combination continues to amaze me. Boat ran 110mph on the limiters with the 29"s. Ran out of adjustment on the jackplates. I am confident there is more speed yet to be had but so far could not be happier.
My goal of hanging with the 28's with 300xs's has been accomplished. A few more set up tweaks and the 400r Skaters better watch out. Some stock 300x motors will give them all they can handle.

Great work Ron. Just when I have started leaning towards the 400R's you pop 110! Now what to do???

500R's ??? ......... Congrats Ron. :-)

Two Strokes ! Keep digging

Very respectable run, and at 85% humidity, and on the limiters, there is more on the table. Nice.

Think what that thing will do in some magic water, with some magic props...

Congrats Ron, Very Happy for you. How high did you run the motors during your recent tests. I really think my rig needs more setback and the motors can go higher when they are farther back. Needs more set back ha thats funny. I really have no setback at all. Not gonna mess with anything at all this summer. Set Back will come over next winter. Definitely can't go as high as you. your water pickups are awesome and its nice to know you don't have to really worry about pressure at all anymore. Slip started going up for me at the two inch mark but my motors are only 3 inches back. Good luck with your testing. you're doing great. Steve.