I have always made single piece guides from delrin and have not had any failures to date. I have come across a failure though ... separated at the end. Also a guide where an unfinished spring end had ground its way through the guide body just in front of the flange.

But I keep telling myself I must make a 2 piece guide next time I need one ...Why? less wastage on material and because of comments on here. Question....if I made a 'bevelled' end flange and guide rod (tube), is there a recommended angle for the end flange. 45 degrees? 30 degrees?
I may well have one or two ex HW metal end flanges so guess I could copy that design.
Cheers, Phil