Ernie.....
I just came across with a truck overfull of furniture, a couple of days ago, plus a bunch of new stuff.
I just showed them my MEX visa (old fm-2)
and said it was for my house in RP.
They said ok, and go.....no Mex tax.
All my furniture was wrapped in black construction plastic. I cut a slit in one so they could look.
Maybe its the luck of the draw, but your allowed one big load if ya prove resident of Mex, I think.