I have the 2510 with twin F115s. With the weight of two 4-strokes, the center of gravity is further to the rear, and the factory 12" x 12" tabs would not push the bow down enough to get a decent ride in the Ches. Bay chop.
I was going to go to larger tabs, but for $65 a piece, I installed a
Cobra Marine plate to each F115. Made a world of difference, and the tabs are much more sensitive.
The plates are solid SS, with a slight downturn to the trailing edge. They bolt to the bottom of the anti-ventilation plate, and thus don't weaken the anti-ventilation plate like the Doelfins do. The Doelfins bolt to the outter edges of the anti-ventilation plate, and over time, the flexing eventually breaks the anti-ventilation plate. The Sting-Ray hydrofoils have a similar problem, because they bolt to the top of the anti-ventilation plate. The Cobra plates, because they bolt to the bottom of the anti-ventilation plate, use the full surface of the anti-ventilation plate as support, and thus don't flex the anti-ventilation plate to the point of weaking it.
The Cobra plates are similar to, but much cheaper than the Permatrim plates. The Permatrims also bolt to the bottom of the anti-ventilation plate, but are narrow and long. The Cobra plates are wider. Not sure which ones work the best, but the Cobras are quite a bit cheaper.
In the end, the plates solved my problem, and allowed me to stay on plane all the way down to about 14 mph--plenty slow to handle some of the big chop in the Bay.
I lost about 1 mph at WOT, but gained about 4 mph slower planing speed and better control.
Here is a link on Cabelas for them (bottom row of pics):
http://www.cabelas.com/cabelas/en/templ ... atcat21276