adding bottom width... suggestions?

[firstinfireman]

I have a 20'x 36" aluminum tunnel hull boat for fishing shallows and running marshes in south louisiana during low water periods of our duck season. i am looking for ideas to add some surface area to the bottom(width) i was thinking of having some 3"x3" aluminum angle welded to make it a 20'x42" boat but wondered how you guys thought it might affect performance. What i am looking for is a little more planing surface to get the stern up out of the water a bit more on plane as well as decrease planing time. I cant use trim tabs due to mu low water conditions.