The topic of “long shocking” frames is one we hear a lot. Frame manufactures like Santa Cruz with their Hightower, and may others specify shocks that have limited stroke for their eye-to-eye measurements. There are most definitely reasons behind limiting stroke and considerations should be made before tossing a 200 x 57 shock on your frame specified for 200 x 51. (or 210 x 55 swap for 210 x 50 / 230 x 65 swap for 230 x 60)
The biggest issue with using a shock with a longer stroke is that during bottom out, the longer stroke can ultimately cause interference, usually with the wheel and the seat tube. You can imagine what happens when tire tread finds the frame… stop-age of the wheel + forward momentum = a bad time.
That being said there are a lot of people who have found success with the modification. We STRONGLY advise you to confirm with your frame manufacture prior to performing any modification.
What we have been able to achieve is splitting the difference. i.e. 200 x 54, 210 x 52.5, 230 x 62.5. This allows the piece of mind and ability to run a higher profile tire. shoot us an email to see if it could be right for you