I have an early 80s Fender bass case which has a split alongside the handle. I've not attempted to fix it yet as it currently lives in the loft. I have seen various youtube videos which show how to fix splits in ABS (car bumpers etc) and the variety of different solutions has put me off attempting a fix in case I chose the wrong method. I'm torn between using a soldering iron with an old (but clean) bit to melt the plastic together, possibly embedding staples to hold the crack together, or using a solvent — eg breaking up pieces of spare ABS and dissolving it in acetone to make a kind of slurry/putty that melts into the area around the crack and holds it together. I'm not convinced though by the method that uses black cable ties, melting them with a soldering iron into the crack as I'm fairly sure that they are made from nylon rather than ABS.
For a crack in the foot area of a Ric case, the Rickysounds kit looks like a no-brainer and should make for a tidy repair, but I would probably be inclined to also use the soldering iron method to seal the crack to (try to) prevent it from spreading further before fitting the parts in the kit.