is there anything stamped in the very front of the lower where it bolts up

Is that stamp at the rear , Id say standard, did the lower come with that stud and and nylon nut ?

Couldn’t say. I had a reputable shop (MDG Performance) install it. Went in for a rebuild of my xr lower and it was trashed. Case couldn’t be salvaged, so we got the imco.

My drive guy told me to put an allen head bolt in the rear spot so it would not protrude below the drive case because it could cause cavitation, I would pull the stud and nut and put an allen head bolt in its place and go test it, even Imco's installation guide there cavi plate for the drive shower said point the bolts upward to prevent cavitaion

That’s a possibility. Cause even when I get on plane it still doesn’t feel right. Feels like the prop is slipping. I even checked to see if the prop was spinning. It feels that loose.

So I guess I’d have to drop the lower to change the stud

No, remove the nut and and take a pair of pliers or double nut the stud and remove the it,

Searching some threads here with IMCO lowers... Just curious if this was resolved or not? Not necessarily having issues with plaining, but prop slip.

One of the things mentioned was the bolt on the back securing the upper/lower units. I have the same setup with the bolt and a nut on it. Will be worth trying an allen head bolt.

I do have a drive shower and mine is on the left / port side with a left-hand prop. I'm going to pull it this spring and do some testing without the shower pickup.

Any other considerations with the IMCO lowers? Mines just a standard height -0.

Thanks