So I was going to attempt this upgrade - MPCNC Modding XYZ Burly Full Aluminium Update - YouTube - where he replaces the core with some linear motion bearings.
Picked up two of these - SWA16UU pillow block linear bearing TWA16 SPB-16
But they feel much too tight for my stainless steel tubing, couldn’t get them on and ended up popping out some of the bb’s. Did I get the wrong thing or is the precision of these such that my tubing is beyond their tolerance?
Most disappointing…
In fact looks like he used adjustable bearings, perhaps that’s the difference, how much wiggle room would an adjustable 1" bearing provide?
I just can’t imagine regular stainless has a chance at working for that. Those bearings need a very precise surface or they get crunchy. And the balls are hardened, so they will start to wear a groove really fast. I don’t advise this at all.
Hmmm - fair enough, that’s too bad though because it looks like a good idea 
I think the adjustable bearings would work as long as you didn’t crank them down too hard. Basically the same we do with the current parts, but the contract area will be spread out over the length of the bearing. You definitely want stainless or DOM tubes for this.
I’m using stainless steel tubes, will see if the adjustable one will fit but given Ryan’s warnings now i’m not so sure 
Ryans advice is solid, unless you are using hardened and ground chrome bar (hydraulic ram shaft basically) they will just get eaten up, and you would have $500~$600 in the shafts alone.
So regular stainless will just get eaten up because the bb’s inside the bearing are so hard - got it - rats…
I mean, it’ll get eaten up with the bearings we have now if you tighten them too much. I just don’t know how loose the adjustable ones are.
The machine has been running for over a year without any problems. If necessary, the bearings can be tightened. I can only do the conversion.
So I got some IGUS l150 filament and printed a pair of IGUS style bearings that fit perfectly and I’m using adjustable pillow blocks, going to give them a try and see how they work out.