how do you do this???

Don't know if even with +5 long travel you would have enough room without changing upper mounts also. Even if you had +5 with the mounts as far out as possible without higher and wider mounts the shocks would be at the wrong angle (layed down to much). Good question tho because I've been mulling this over in my brain also.
Out of curiosity what shocks were you looking at?
 
I had trx 450r shocks on my blaster , and they never would have fit on stock arms , I had asr LT +3-+1 Arms and they fit perfect , but were only 16" I think. why such a long shock? get a set of corect length fox floats or Pep progressive rate shocks.