You pretty much got it,,,as long as the forend is shimmed so that the only contact with the barrel is at the screws or at least behind the front screw. I know some guys that use up to a 1" wide strip, the length + 1" of the screw spacing, cut from milk jug plastic. Works pretty good from what they say.
You don't say what forend(s) you are using, But when it comes to wood, even the hard synthetics, assuming a proper fit, I just sand out the sides behind the screws, and in front of the screws the whole channel. I still want a fair amount of good solid contact from the front screw back on mine, I don't use shims or hanger bars of any kind. I concern myself more so, in the area of the forend "ears", that could come in contact with the frame. I make sure there is some gap at those points. The forend always has contact with the barrel, so in the true sense, it's not really free-floating. But opening the barrel channel would eliminate possible contact ahead of the screws, should the barrel walk a bit from heat-up or natural barrel harmonics.
Shimming basically just replaces sanding, which works fine. No matter what you shim with, just keep it on or as close to the screws as possible. Although, personally if I was using tape, if it's more than one thickness , I would go to something firmer for solid contact. If I was really concerned with the forend beyond the "ears" contact, I would bed it with bedding compound from the rear to a 1/2" past the front screw. This would eliminate any possible movement due to shimming or not so perfect sanding job, between the barrel and forend.
Dave
