Your doors will actually glide better on the plastic glides versus a dado in the wood.
The 1/8" doors are sometimes made from tempered Masonite.
I prefer a 1/4" panel of plywood.
There should be no warpage with either of these thin paneled doors.
My Dad liked to build cabinets with sliding doors in the '60's.
He used both the plastic glide and the dado.
The doors width should overlap by about 1".
The doors can be removed if needed by lifting up out of the channel.
Good luck to you.
I have some furniture from the late 50s/early 60s that uses 1/8" hardboard (AKA Masonite?) for sliding doors and it is perfectly true with no bowing at all.
Sounds like your dad used to make cabinets the same way that I'd like to!
Good to know that the plastic guide can be / has been used before. I also thought about using UHMW tape (non-friction tape) in the tracks as well as on the bottom of the sliding door. This might be even more slippery than using the plastic track, as well as more concealed.
Without being there it's difficult to tell the exact construction. I think it's sheer luck the doors on the 60 year old cabinet are still usable. There isn't any reason to ask for trouble. There are a lot of stable materials a person could veneer over and make look like wood. A person could even veneer over a sheet of plexiglas or even glass. This would guarantee a door which would remain flat.
I do know 1/8" plywood is nearly impossible to prevent warpage. It's normally used for the face sheet of a door which is either solid or hollow with cardboard tubes in the center to bond both sheets of each side of the door together. There is a type of veneer which is actually formica with a wood face on it. If the thin doors were laminated on both sides with this type of veneer it would add a lot of stability to a thin door. If it also had a MDF core to it that would make it even more stable.
Thanks again for your input. Am I correct that it is probably a question of how tall the sliding door is? Obviously a very short sliding door (say 4" in height) won't bow, even in 1/8" plywood, right? So then the question is at what height would it become unstable?
I agree that there is no sense in asking for trouble by using material that is too thin. But I'd like to find out if I'm really borderline for wanting to use 1/8" sliding doors of about 24" in height. They will simply look better and slide easier if they are thinner rather than thicker.
I wouldn't push the issue if it weren't for the fact that I seem to see lots of furniture that uses such a design. Come to think of it, of all the shopping and browsing I've done for mid-century furniture, I've never seen a sliding door that was bowed.