How to weld on a 2" Receiver onto a trailer tongue?

I'm looking at this Lock and Roll hitch, that has an extended trailer side connection.
https://locknroll.com/shop-now/trailer-side/kayak/
It is designed to go inside of a 2" receiver hitch.
I'm getting ready to build an offroad trailer, and I like the idea of being able to keep that longer design tucked inside the trailer tongue most of the time, and being able to slide it out and re-bolt it if I need a longer tongue. (for adding bikes or firewood, etc onto the front of the trailer for non-extreme trips) I would like to just tack some 1/16" shims on the outside of this receiver (2.5"x2.5" outside dimensions), slip it into a 3x3x3/16 tubing and fill in the groove between the receiver collar and the end of the square tubing. However, the seam weld on the 3x3 square tubing will probably interfere, so I may have to just cut that out and plug weld between the 3x3 and the receiver.

I just can't figure out what the "normal" way to add a receiver onto a trailer tongue is.