OK here's another scenario: I'm on finals to land and think I'm going to overshoot - I stick the nose down let the speed build up to above normal approach speed, I then pull up to regain normal landing speed. Would I still overshoot or because I've effectively gone outside of the best glide speed reduce my range to touchdown?
One way to combat an undershoot is to lower the nose and speed up. Especially if the undershoot is caused by headwind or a bunch of sink. For a headwind you need more speed to make progress over the ground. For bad sink you want to fly fast to get out of it. The challenge of speeding up for an overshoot is you end up with a bunch of kinetic energy that has to be disposed of. In short, I agree with Crash one.
On the other hand, I've recently bought and have been flying a SGS1-35C. It is a flapped glider and has no spoilers. The flaps go down to about 80 degrees and cause a boatload of drag. You can really modulate your glideslope by changing speed. If I am high, and not on short final, I can really point the nose at the ground and lose altitude rapidly without a large speed buildup. However, what I am finding is to get back on glideslope, I dive down below it, then as I slow up my performance increases again and I will get back to glideslope. I'll shoot my final approach once I'm stabilized again about 55 mph, though the glider won't stall with full flaps until 35 mph. Makes for nice low energy landings.
Regarding the original question, in either power or glider I prefer to slip on the higher speed side, rather than risk an uncoordinated stall at low altitude. In either a glider or a power plane you can always hold the slip through the flare in ground effect, where you have greater margin over stall. Then again, like will5023 said, maybe it is a problem of perception rather than being at a high AOA.
-- IFMU