It's been a while since I did my initial edits to Moldovers BLU, but I think in the end I turfed the STAC bit.
I hacked the scratch function down to something really simple. It's good enough for my needs (which rarely involve much scratching - just a quick scratch forward or scratch back sound, then back to my track) but maybe not good enough for yours.
I set it up so there's a 'scratch-on' button. If I hold that it's like I suddenly put my fingers on the record and stopped it. Then I can scratch 'up' or 'down' by holding the keys to either side. Up is an accelerating scratch, down is a deccelerating one. If either key is held long enough it's like a tape recorder zipping forward or back at high speed, and doesn't sound very scratchy anymore, but used briefly, these combos are good for that 'I just gave the record a tweak' effect.