Young distiller

I've heard small amounts of glycol or glycerine can soften up your spirit. Was looking online for the answer, but adding either product will thicken up your spirit, how will this affect your ability to get a correct hydrometer reading?

@Distiller76 I was just double checking since my dad has owned this distillery since way back when. He was under the impression it was +/- .3 and of course looking it up myself i didn't find +/- just -.3 proof. Wanted to double check.

First of all, who ever put this site together, great job. Have been reading through it and it's awesome to have a forum that answers most of our questions rather than trying to call the TTB and rarely get a straight answer. Ok, so curious if any other small facilities have had this issue. QUICK BACKGROUND: We filed for a new permit since we wanted change owners, father to son(we've had this small distillery for 20 years). As ttb came out to do there investigation they took 2 bottles to sample. We were told both bottles were at 81 proof not 80. Although we sent samples to another TTB certified lab and they gave us a reading of 80.23. Our inventory was only about 15 cases. Again we're a small distillery and we only bottle 6 to 12 cases at a time. Basically bottle when we need to. So end result the TTB investigator told us to stop all operations until the new permit is complete which will take another 2 months atleast because we were over proof and that didn't match our labels of 80 proof. We have one major account we can't afford to lose. Has anyone other distilleries gone through something similar? What did you do? Also, for some reason the TTB investigator didn't know the answer to this but does anyone the tolerance +/- you can be for spirits(Vodka, brandy)? is it .3 proof?