I converted an old steamer trunk into a humidor, Do you need to season it just till the RH gets to 65% or longer

You converted teedubbyas butt?

Get it stabilized at what rh you want to keep it at and hold it there for 4 or 5 days to make sure the seal is good.

Should I put a gasket around the lid to keep it airtight

Lefty, if it's not cedar (spanish) inside, the wood is going to absorb moisture at all different rates and give it off pretty fast. My want to consider dropping in a thin layer of spanish cedar (non-aromatic). It should have a good seal everywhere also. Correct me if I am wrong but I think the old steamer trunks were made of pine with hardwood strips on the outside to give it some strength and durability. Not the best wood for a humi.

Like was mentioned before, leave it empty and get it to where it is holding the fh you want consistantly for a week or so. Then you know you will be good to go.

I lined it with spanish cedar and have two lbs. of beads in it 65% been 4 days holding at about 63% according to digital hygrometers, its seems to seal pretty good but does it need to be airtight?

Also built a shelf with 1/2 in. cedar and left some gaps between the pieces for air flow. I'll try to post a picture of it soon

Doesn't necessarily need to be air tight but should be real close. Sounds like it's almost ready!!