Well I thought I should use solid blocks, so yeah I think the inserts are a good idea. Even if they are overkill if they prevent a catastrophic failure they were well worth the work. Think about all the lift blocks you've seen for 1/2ton pickups they are usually solid or are built like a masonry block with lots of vertical support, if 3/16 wall square tube would work they would have been using that years ago. So yes I like your tubing idea and yes I like the tubing inserts and caps welded on too, and I don't have access to any solid stock anymore, now I'd be at the mercy of a heavy fabrication shop to cut me the blocks I'm sure I can get a couple feel of tubing for what 50$ that's easier than what I had in mind.