Yeah... I'm a bit annoyed as I don't want to fit the chain and then find out it won't work properly, necessitating both a new chainset and possibly a new chain (I'm a bit unsure about lengthening a 10sp Ultegra chain once it's been shortened).
There's no 52/36 6601 chainset so I may have to bite the bullet and go 52/39. I'm usually cool with 34/23 on the steep stuff so 39/28 (yeah, it's a 12-28 cassette) might actually not be too bad. It's pretty rare that I use 34/28. In fact, just writing that ratio makes me disgusted with myself. HTFU it is.
Cant you just get the chainrings and EBay off the ones you have?
I'm assuming 110 5 arm pcd here. But I'm no shimano expert.
See the BBB ones....
http://www.cyclesportsuk.co.uk/index.php?cPath=522