Hi Higgo, I’m the brand manager at Spank. Sorry to intrude in your forum, but maybe I can help.
The inner width of an Oozy rim is 21mm. Spank sells an ultralite tape called Fratelli Tape, which is 25mm and perfect. Sounds like it would be too wide, but you want to make sure you tape all the way up to the bead hook on the vertical flanges (side walls). When I convert an Oozy rim with our tape, I go all the way around on the right side right up to the bead hook, then cross over and go all the way around again on the left side (up to the bead hook). This seals the joint (which is sleeved for strength), and provides a better seal under the tire bead.
As Ruscle mentioned, many of our riders use ghetto set ups like gorilla tape, or a BMX tube cut to the right width. We suggest an adhesive tape as it tends to work a bit better. If you choose a thicker heavier tape like yellow strips, then you may get away with one lap around the rim, but you do need to watch that you seal up to the bead hooks especially at the joint area.
If you have more questions, you can email me at mike@spank-ind.com