F#Sonata is correct VMS allows you to stretch events by +/- 4 x. With Pro you also get velocitry envelopes which allow you to stretch by a further 3x (thus giving you 12 x in total in one pass).
You are correct in that the way to speed up more is to keep rendering. But this isn't as bad as it seems:
1 pass = 4 x.
2 passes = 16 x.
3 passes = 64 x.
As an alternative, you could simply delete 59 out of 60 frames which might be a bit tedious
