Hi Vonmarshall

the little H/Long pz3 is a really great runner and the asiatam hull will only enhance the drivability of it
just a thought have you looked at the Taigen lower hulls?
these are a direct copy of the asiatam hull with a few mods and a local seller Dave (Forgebear Tanks)sells them

if your only after sounds then the cheapest option would be a beier sound card but if you want to go battling with a tamiya type battle system then something like the SLU or the DBC and benedini sound card is another option

i will agree with not adding too much metal as it does put a strain on the electronics

hope that has helped a bit this stuff is really a minefield when you start looking into it

Rob