What you need to do is raise bike on lift and remove the rear shocks then measure the eye to eye distance of the mounting points to see if there is enough room to fit them with out the front of the swingarm hitting against the fuel tank. That is what will limit the length of shock you can install.
I did some geometry studies years ago, with the same interest in mind and discovered that a 1/2" longer rear shock would actually raise the rear end nearly 1".
Of course after I installed the aftermarket 5 gallon tank in my '04 the swingarm no longer had room to allow enough movement so I wasn't able to fit them.
The cross member of the swingarm in front of the tire moves up and down in a molded notch in the rear side of the plastic tank. It only has so much room to swing in.
Check it out before you spend good money on something that won't work.
One thing you can do is slide the front forks down in the trees a 1/4". Not much I know but it is at the front of the bike where the footpegs are which are generally one of the first things to touch down.