Sorry I took a while to get back to you.
You can easily loosen the belt tension from the top/side.
Please see the attached photo. Take a regular size 3/8ths inch wratchet wrench and insert it into the tensioner with the wrench handle at the 1-2 O' clock position exactly the way it is in the photo. Take your right arm in between the upper coolant hose and the alternator and grab the wrench. I was easily able to pivot the tensioner clockwise with my right arm and lift the belt off the pulleys with my left.
In retrospect it might have been easier if I used a 3" extension but thats all about whether or not it pushes the wratchet wrench out too far towards the coolant hose or not. Either way it was really easy to do it exactly as described.
KB 2.1L | Stock F. Pump + KB BAP | KB CAI w/ 90mm MAF
MAC O/R H 2.5" | Flowmaster 44 CB 2.5"
Tokico D-Specs | MM FLSCFs | J&M S/S LCAs | UPR S/S UCAs
Nitto NT05 315/35/17 | FR 3.73s
Totalled 1/25/2013 | Rebuild/Full Paint Completed 6/15/2013
Mustang's 50th Anniversary Charlotte, NC 4/16/2014-4/20/2014