I use strips of lead flashing, glued on w/ contact cement or spray adhesive, & covered w/ electrical tape.
You can use just tape initially.
Tennis shops sell adhesive lead strips for weighting racquets, but you need ~10g for a wheel & the tennis stuff is pretty thin.
My feeling is that if it reduces chance of pants-filling speed wobble, it's worth considering, and with the added 20g, the bike is still barely over 15 lbs.
I have a big roll of the stuff, & will send a piece for postage.
