I have done this several times and can say it works GREAT! Ok, well... if you have access to an LCBH Clownface, (or figure with a similar midsection), and you aren't worried about making it into fodder?
First you'll need a dremel with a cutting wheel or a hand saw, an awl or icepick, and a hammer! Please remeber to wear proper safety gear! I forgot to put on my safety glasses once and spent the better part of six hours getting a small sharp bit of red plastic out from underneath my eyelid, so, if you enjoy your eyesight, heed this warning!
A dust mask, safety goggles, and gloves should be sufficient but always remeber to be careful as you will be working closely with sharp objects and/or power tools. Kids please, get your parents permission and be sure to ask for assistance if possible.
Take the Maestro Hulk put the awl in the center of the abs. Strike with the hammer to free the upper torso from the existing abs. Careful not to break the joint in the upper torso.
If you look inside the abs you can see the swivel inside where the factory melted the abs to the pelvis. Don't worry it's only attached about halfway through.
Remove the plastic spacer from above the upper torso joint peg using an exacto or wire cutter.
Next use the dremel to cut the abs from the pelvis being careful not to cut the swivel joint in the center as you may want to modify and use that, or you can use just about anything from Clownface's swivel to bolts and washers.
Then, carefully crack open the midsection you removed from Clownface and remove the joint peg. Turn the back half of the midsection sideways to slide onto Maestros joint. This is the only way it will raise up the spring high enouh to attach. Lay your modified hip joint inside Clownfaces midsection and attach the front half.
Be sure to glue all pieces once they are in place.
You can replace the knees or legs with almost any Hulk-sized figure.
You have now made the Maestro about the height of Abomination. If you opted for FA Gray Hulk knee and lower legs retaining the feet of Maestro, you now have a figure that looks down sadly at the poor, pathetic, Abomination with his lack of ab articulation. Makes a pretty mean Terrax!! Hope this helps! If you have any questions feel free to ask.
http://redrebelcustoms.webs.com/apps/videos/