It depends on the brand. I find Mattes have the neatest GP cut which works well on most WH/VSD saddles, better than most (rather awkwardly shaped) GP pads. How is the cut at the front? I wouldn't worry about it being too long in the flap apart from actually in the show ring (are you showing?).
Some brands do WH cut I use the nuumed dressage ones on my show saddle but it has got an extra long flap so they are fine but I wouldn't be too worried of the length for everyday.
A lot of showing people I know use the pollypad squares for everyday.