After experimenting with a 3.7 Plastic TB this weekend I was able to confirm that they can in fact be hand-ported. Previously I didnt offer this as I was worried about the plastic melting/warping.
The new TBs will be 69mm both front and back, with a stock blade. This is a huge improvement over the stock measurements. Pricing will be competitive with other TB vendors who only taper-port the inlet only.
With our old taper ported inlet 3.7 Plastic TB, we had excellent feedback, I would expect further gains with the backside porting as well.