I madde3 my own tree sliders but then again i am a time served welder,
To clean up the inside of the out rigger i used a wire brush attachment on a Air die grinder to remove all of the crap, But you could use the same attachment on a drill. Then applied rust converter, red oxide and a good spraying of shultz, Left to dry for a few days then covered the bit of the tree slider that was being inserted(pipe) with copper slip.
Once everything was bolted up and sitting in the right place i drilled through the out rigger and put a M8 stainless steel bolt and nylock nut on to keep the slider in place. I have see some being pulled out when off roading and buckeling the plate that bolts to the bulkhead. That part of mine is made from 6mm angle iron instead of flat bar so that it does not twist.
Mines have taken a right kicking, even had a winch connected to them to stop me from rolling over while i winched myself out