I wouldn't go with an Inland Surfer skim if you want the fastest. They are on the slow side for skims in my opinion.
The new Phase 5 Danielo Diamond is supposed to be really fast. The diamond tail keeps the board higher out of the water than a pin tail which helps make it faster, but also makes it looser.
Victoria makes a re few wakesurf skims and they are really fast. They are amazing for the money. They sell for $379 and are really fast down the line. They are a bit sticky for lip tricks, but i think its due to the flex. They also make a carbon board which would not flex like the cheaper one.
And I know I always mention it, but Calibrated makes an amazing skim board. They are really quick and very responsive. They are a small company that I think will grow once more people try them out.