To optimise your gapping, you must kick right when the rear hub is vertical to the rail or gap edge, and when the bike is nearly horizontal. But when you balance on a rail, you're not horizontal at all, and lowering the front wheel actually rolls the rear wheel forward by about a foot (and the rear hub beyond the edge). That's why a backward readjustment hop can be handy, so that when you lean the bike forward, you end up in the perfect position to kick in the pedal. Once you can visualise that, you know exactly what you do. Very often, if you land right in balance, then the pedal kick will lack of power if you don't do a readjustment hop backwards. It 's not just the bounce effect I am talking about. If you don't want to hop, then, you need to land with the rear hub slightly behind, with enough momentum to carry on and lean the bike to the perfect position (that brings the rear hub right at the vertical of the rail) Something I realised when trying to gap further.