Ironwings, you might not want this idea either but here goes...
Cable crunches on the lat pulldown machine: Use a rope attachment and stand facing away from the machine, straddling the bench. Push abs out and harden them as much as you can. Then pull down to 90 degrees.
Doing crunches this way allows you to go heavy. You can rep as low as 6.
I realize you don't want to end up looking thick, but this might provide the plane of travel you need.
One more thing is you could use bands to provide resistance instead of using the cable. I'm thinking this would allow you to customize your range of motion. Found a picture:http://asp.elitefts.com/qa/default.asp?qid=37622&tid=101
Cable crunches on the lat pulldown machine: Use a rope attachment and stand facing away from the machine, straddling the bench. Push abs out and harden them as much as you can. Then pull down to 90 degrees.
Doing crunches this way allows you to go heavy. You can rep as low as 6.
I realize you don't want to end up looking thick, but this might provide the plane of travel you need.
One more thing is you could use bands to provide resistance instead of using the cable. I'm thinking this would allow you to customize your range of motion. Found a picture:http://asp.elitefts.com/qa/default.asp?qid=37622&tid=101