As an ITB guy, I say move as many down as you can.
It sounds like there are a few different models currently classed in ITA that dont really compete...

Move em down now with the readjusted weight. Sooner the better.

This isnt pro racing. None of us are pro racers...we arent winning anything here (except bragging rights...which is really kinda worthless).

So, if a mistake is made in the reclassification from A to B, readjust the very next year! Get it close and go with it!

This can only be a good thing for field size, perhaps encouraging guys with uncompetitive ITA cars to get out and race more.