How well do the 8020 UHMW slide bearings work?

I'm planning a large router, like maybe 4ft x 5 ft. The linear bearings may be quite expensive. But the frame will be 8020 so there's slots which could take them. In fact I have a working mill and UHMW stock, not hard to make some.

But will they work? I'm sure they add some friction, may have some slack, and won't last forever. I could always replace them with some sort of proper linear guides later, but of course if this is a waste of time then it's a waste of time.