Common, but hack
You'll still be left with lousy travel, and very bouncy shocks since they will be about 80% compressed all the time, permanently squahing the springs and weakening them.
Harold's idea with the revo shocks is good- seen that done with normal maxx arms and towers, but again, since you're using GM towers and normal arms I strongly recommend playing with the tape measure; this isnt the sort of thing I or anyone could guess at to find the best length shocks.
One last thought is that if you go to fleebay, you can pickup entire GM rollers for the cost of just the towers sometimes, which is well worth concidering...