Whilst you're adding time to levels, add some to Lemmy's castle (that is the one at the end of the Ice World, right?) If you fall whilst ascending the note blocks, its very very difficult to get to the end and defeat Lemmy in the current time limit.
Oh and something I posted in the Help forum - for some reason, after defeating Bowser, pressing up whilst at the flashing door doesn't end the game - you have to press up at the left pillar instead. Could you fix that too?
Having gone through all 70 levels though, I absolutely loved the hack - it was amazing. It kept me more entertained than NSMBW (at least until I started playing it by myself rather than multiplayer).
Any plans for another hack?