"Heatshrink?" (Chokes on his tot o' rum...)
Heatshrink is for Boatrace rowing! A well-found oar (not blade; blades have heatshrink) should be leathered. A bit of a b### on ali shafts, for sure, but on nice wooden oars it will be absolutely perfect. Especially when finished with copper clouts and a nice turks head either side to stop drips running down the loom. Copper clouts are not negotiable; anything else is going to muck up the crutches or shred the leather.
Heatshrink probably needs some sort of key to locate it, because the last time I redid some blades they were gorgeous old Aylings- pre Dreissigacker- and the sleeves were hell to fit because they were about 3mm thick when they had shrunk down. The sleeving needs to be locked in place by corners or something, so new round shafts have clip-on sleeves which seem to stop the sleeving from sliding. Also, getting hold of big heatshrink tube commands a huge price premium because it sells in minimum lengths of a metre.
Go with leather!