700c Velox is always long enough for 27" rims, with considerable overlap.

The kind of tape that might work depends on things like air pressure and the size and configuration of the holes in a double-walled rim's "inside" wall.

Some rim tapes just cover up the spoke nipples, but must withstand the possible cutting effect of sharp edges if the nipples are turned while the tire/tube is pressurized.

Some adhesive tapes use an adhesive exposed along the edge which can permeate the tube and cause splits. I've even seen cheap OEM rim tapes do this.

Modern snap-on fabric rim tape bands are the ultimate in convenience for use with double-walled rims, with no adhesive to rely on. The tension in the band gives support for resisting air pressure pushing into the spoke wells.

Rubber rim strip bands for single-walled rims often split at the valve stem, so I install them with Fast-Tack to either side of the valve stem and they stay put during tire changes.

Any thickness of rim tape that extends "wall-to-wall", to the junction of a non-hooked rim's sidewall will serve to increase the inflation pressure limit of a wire bead tire on a given rim, but adding thicknesses of tape also tends to make tire fitment more strenuous. Most straight-walled rims don't need the help.

Particularly with aged adhesive tapes, there is a tendency for the tape to migrate sideways, which can expose the spokes/nipples/holes, and can interfere with tire's bead seating on hooked-bead rims, possibly causing blow-off.