Nice clean tear - easy to fix.
Don't use epoxy - too heavy. Rubber/contact cement only if it's a poly cone vs paper. For a paper cone like this one use regular white/school glue. Water it down a bit so it doesn't go on thicker than necessary, dries slower, and paints on with a brush easier (though sometimes I just finger it on). Alternatives include Wood Glue and Modge Podge (in both cases def water down) - both being water based as well and very similar.
Paper towel is a bit thick - I use toilet paper (if thick/multiply, use a single ply). Layer of glue on both front and back, line up the tear, stick on TP patch on rear only ( don't want to see that from the front), and then paint over the patch with another layer of glue (watering it down as mentioned also helps is not rip the TP when you top coat). Optionally another coat on the front as well if you're worried it's not strong enough. Be conservative with the glue - you can always add another coat later.
Basically you don't want to add significant weight in an unbalanced way. That can be bad. Adding weight in a balanced way (e.g. paint the entire cone with watered down glue/mod podge) is a common mod in DIY HiFi circles for cheap drive units when you want to lower the resonance/bass response and don't mind risking the loss of a bit of high end (cuz there's a tweeter for that anyway). I've repaired many a low power vintage alnico this way (reconing is not worth it - costs more than replacing the speaker). After a few you even learn to make them not so damn ugly.
