@Allan.
I usually try to cut the length of cable at whole wave length times the velocity factor of the cable (e.g. 0.66), to limit possible mismatch/standing waves. Easy to do that with a dipole or 1/4wave, but not sure where to start measuring with a sleeve aerial. At the middle of the dipole, or at the end of the braid.
I guess at the end of the braid, because the braid is part of the balun.
Maybe you can answer this.
Leo..