First, you cut the frame to the hanger or more the hanger to the end of the frame. Then make sure nothing else sticks out past that. Hate to be captain obvious, but anything sticking out is putting a limit on you. You can see what I did to avoid it.
Second, figure out if you can move the axle on the spring toward the ends. This asymmetry causes changes in behavior like increased axle wrap and pinion rotation in travel. It also causes increased bind through the axle housing as each spring wants to torque the tube in opposite directions when twisted.
Third, figure out if there is some way to use a different leaf and/or mount to achieve the same flex with less overhang. That's how I wound up with my reversed 57" springs. However, that impacted lots of other stuff I had to deal with like axle wrap and pinion control (it rotates exactly opposite what you want). To fix that I had to add an anti-wrap bar and use "Springer/AK57" shackles to let the short end (now in the rear) swing down, simulating a much longer spring like the 63"s.
Down side is that the rear springs don't last me any time at all any more since I kinda got interested in "climbing waterfalls". Worked fine and lasted a fair number of trips till I started trying some of the really nasty climbs.
But, I got nearly 90* out of leafs. Not sure the ultimate performance and trade-offs were worth it though. It's sure helped in a few cases where any longer "departure" angle would have made things much worse for me, but I doubt I would work so hard to get it again. If you really care enough to go to that much trouble, save that wasted time and trouble by going links as I am.
