First I want to thank Tom Kirkman for his excellent solution of raising the seat with 8lb expanding foam. It was this great idea that brought my adaptation to reality.
I will post his solution for it, since it is the prelude to my finished product.http://www.youtube.com/watch?v=rrdT0gzQPww
Where I strayed from his original concept was to eliminate the PVC sleeves. I found the self draining scupper plugs by Ocean Kayak at my local kayak dealer and saw how they could easily be utilized. The scuppers are a purge valve design. The purge valve is held by a retainer snapped into the main housing with an o-ring seal. The entire valve is 1-1/4" in diameter but too long to be used in a Hobie scupper.
I raised the seat with the foam letting the foam fill the scupper recess. I taped over the top of the scupper plug flange opening with painters tape so the foam would not lock onto the plug. I taped over the seat peg holes with painters tape. Sprayed the seat well liberally with silicone mold release and poured 8 ounces (4 oz each of foam and activator) total mixed and let set for 20 minutes. I then poured 2 ounces ( 1 ea.) of the mix from a squeeze bottle to fill in the perimeter. The mix sticks quite well to the seat even with the mold release and it takes some careful prying to lift it out.
The foam seat was sanded down on the street asphalt in front of my house as in Tom's video.
Once out I drilled the scupper opening with 1/4" pilot hole through from the bottom centering on the scupper recess. Note the scupper plugs are not centered so center on the entire depression. Using a 1-1/4" hole saw I drilled through following the pilot hole.
The Ocean Kayak scupper is too long so I cut it down to flush with the retainer clip. Remove the o-ring. This new cut down valve will be pressed into the 1-1/4" opening flush with the top. The depth of the scupper depression is deep enough that the rubber purge valve will open without obstruction. Keep valves aside till after the seat riser is painted.
I then painted the seat riser top and bottom with Rustoleum Never Wet 2 step process to waterproof it and then painted with a grey primer. Before inserting the scupper valves I put a bead of silicone in the groove of the o- ring letting the bead extend out of the groove. Pressing the valve in the silicone seals around it. I then filled the perimeter recesses around the retainer clip with silicone. Do not get any inside the valve itself.
I seated the riser with silicone around bottom perimeter and a bead around the scupper depressions. My edge was a little high so I sealed the perimeter with silicone flush to the deck.
SPECIAL NOTE: You see I did not use the seat plugs. I have a Skwoosh seat and no need for them. Those that want to use the Hobie seat follow Tom's video for adding the peg holes into the seat riser.
I now have best of both worlds a raised seat (approximately 1" to 1-1/4") to eliminate the puddle and self draining one way scuppers. My choice of silicone does make it removable with fairly easy cleanup.