IMO, a longer wheelbase is a cheat for me to keep a shorter COG without having to adjust the weight around as much to maintain stability. Remember that during the transition period, it's your COG that accelerates to align at the bottom (the brachistochrone problem). So you might get a boost on the slope and pay for it in the transition and flat.Think about a 5" wheelbase car as the front wheels hit the transition point....now imagine the car stopped at that point. Imagine where the front edge of the car is on the track. Now a 4 3/8" wheelbase car comes down....as his front wheels hit the same transition point wouldn't the car have actually traveled a little further on the slope before it's front wheels where in the same spot as the 5" wheelbase car and thus the nose of the shorter wheelbase car be ahead of the longer wheelbase car....ie closer to the finish line.............should be a slight advantage
Either way, a short base is more difficult to get stable on the flat. The wiggles will kill your run.
When I get better at adjusting weight distro, I might try to shorten my base for the reasons you are saying...but I'm not there yet...and you can see Mid-Ataltic and Reece are smoking me and they both have shorter bases but still run smooth as silk down the flat. They also can taper their nose better than I can on a long base car.
There's tradeoffs everywhere though. A longer base has, naturally, a longer moment arm and thus the lateral force the track applies to the DFW will be less. It's like pushing a door open at the hing or at the handle. Same door, but it opens easily at the handle, not so easy at the hinge.