Shimano ultegra 11-28 to 12-32 options? I have a Shimano Ultegra RD-6700 rear derailleur with a 10 speed Shimano 105 5700 11-28 cassette and Shimano R565, 50/34 (compact) up front.

I would really like a larger gear for climbing. Can I go to a cassette with a larger than 28t that would not require a new derailleur? 

I see that in Shimano 105 5700 cassette series only goes up to 11-28, 
but the Ultegra 6700 10 speed goes to 12-30. Is there another cassette that I could use that goes to -32t?

How can I tell if I have the RD-6700-SS (capacity 33t) or the RD-6700-GS that has the 39t capacity? It only has "Shimano RD-6700 Japan VIA" stamped on the back. It's the one that came with my 2013 Trek Madone 4.5.

I assume that I have to stick with a 10 speed cassette in any case. Are there any options beside the Ultegra 6700 12-30 that would fit?

Any advice is greatly appreciated!



EDIT: I measured the distance between the centers of the jockey wheels, and its about 6cm, so it looks like I do have the short version.

Is it possible to go from a 10 speed to an 11 speed cassette, like the Shimano Ultegra 6800 11-32, without changing the shifter? I realize that I would have to change the rear D to something like the Shimano Ultegra 6800 GS, which says it can handle up to an 11-32.

I didn't see any options for changing the the front chainrings, it seems like the 50/34 compact is the only one that fits this bike.
To use older 10-speed Shimano shifters such as Ultegra 6700 with cassettes larger than 28t, you need to use a 9-speed MTB derailleur.  You'll be able to handle cassettes up to the largest specified for the MTB derailleur (and likely a bit larger).

Shifting won't be as good as a full Ultegra 6700 drive train, but it will work.