Welcome Stefan! Glad to have you here. Not sure about bike inner tube but Theraband is popular for slingshots. The Gold stuff is the strongest and many shooters here use it. I have the Gold from my Fish Hunters and tho a bit short, it is some powerful stuff. I have other exercise latex to cut up soon. It's a good option for slingshots. Cutting it properly is the key. As for Dental wax, funny you bring that up. I had some waxed and thought "I'll try this to tie and see how it works. I put it on My Hunter with a set of flats and it held up well. I just wondered if it would work so tried it.Im not sure how long it would hold up or if the floss is bad for the bands. I can see it being too "bitey" with the bands tho..