Recently we recieved about three inches of rain overnight.  Two poles holding up the custom cover (It fits perfectly on my Jimmy 2 by the way) were in place yet there was enough sag in the cover to let water pool and thus find its way in.  Quite a bit of rain penetrated.  Gallons of it.

With another storm looming I searched for a fix and flat out blundered into one.  Something called a pool pillow.  These things are used to "tent" tarps in swiming pools.  I got a 4 X 8 foot pillow, semi inflated it, and stuffed it down the lenght of the skiff.  It poofed the cover like a loaf of Wonder Bread!  The  storm dumped 2 3/4 inces of rain that night.  In the morning I mopped out less than a cup of rain water.  I took the pillow out and put the pole back in the keep things vented.  When big rain hits however that pillow will be back.  It might work of you.