All this tweaking almost makes you think that the Technics engineers were a bunch of idiots and didn't know what they were doing! This is far from the truth I think, so I'd advise extreme care with these drastic mods and make sure at least one of you actually measures what's going on, heavy platters or not, otherwise in attempting to fix supposed problems, you may actually make things worse. Sonic differences can be mis-construed you know -

Oh ok, I'm coming over all "evil auntie" here, but please take care fellas with what you're doing and maybe buy a spare stock deck with which to compare - those add-on boards cost a heck of a lot for what appears to be on them, so if you can readily afford to purchase these, then you can afford a couple of hundred on a stock deck to temporarily use as a reference, which can be sold on later