Have just succeeded in adding an original walnut buttstock to my Thompson - hollowed out the butt to take a large battery .
Pics of my conversion job - may add a STEP-BY-STEP guide if I get time - pics may help anyone thinking about it but it is not for the fainthearted - very difficult even with experience working with wood and thew right tools - I certainly think the real wood stock is the best in terms of reality, feel and looks - now for the foregrip - think the trigger grip is a bridge too far in terms of difficulty
Hollowed out stock - a lot of hours of work
Slanted hole bored back through stock to allow wires to go through
Butt screw passes up by the wires and - a bit tight but it does it
Battery and wires snuggly in there - its tight
Infairness TM done a good job on their stock for replicating the real wood - but the 'in-the-flesh appearance and feel are the real benifits over of the TM stock or any wood kit
With Butt attached - pic does not do it justice
Tools needed
What did you do for the buttplate?
I did this a couple of years ago but have never managed to attach the buttplate.
The foregrip is a doddle.
Pistol grip is just too thin to enable an original to be hollowed out,
Just screwed it back on - why would yours not go back on ?
Any adjustments needed on the foregrip ??
Know what you are saying about the trigger grip - nothing left to work with.
Did you use a few small washers with the back scre of the buttstock - screw a bit long and does not pull stock up fully - puts pressure on the little boss that the front screw goes into and can break it
Falay
I assume HS means the original TM buttplate.
Incidently a small warning for others thinking of doing this. Make sure you get the right kind of stock. The 1928 thompson stock will NOT fit the TM thompson. I've had one sitting round for about 3 years now 
No longer involved in airsoft.