The result was worse than expected - the tube was not uniform at all on the outside. On some locations, there was a gap in the shrink tape. There, the fibre "escaped" the pressure of the tape and "ooozed" out of the gap. On other locations the tape overlapped and leading to locally higher pressure creating non-uniform wall thickness. I don't see how I could improve the process prevent that other than using less compression force, which would probably lead to delamination inside the tube. A heat shrink tube would not have any gaps or overlaps, but it would still compress the fibre. I guess the fibre would "meander" under the compression force as the outside diameter would shrink a bit.