Another cause of wheel hop is a warped chassis. After struggling with the reason behind the "left front tire off the track" problem I realized it's often the chassis itself that was causing the problem. My solution is to remove the gearplate, magnets, and brushes, grip the front of the chassis in my left hand and and give the whole dang chassis a slight twist away from my body with my right hand. Gotta be gentle since too much twist is a bad thing. Each time I make the adjustment I put the magnets and gearplate back in the chassis and make sure the whole thing rolls on all 4 wheels before doing any additional adjustments. For some reason the left (drivers side) wheel has always been the airborne wheel on my cars. Must be an artifact of the manufacturing and shipping process.
I've done all of the things mentioned above, added heavy brass independent front ends, replacement straight axles, replacement aftermarket wheels and tires, used regular TJet pickups, limited shoe travel, etc., and still had some degree of hop & skip going on. I truly believe that the oversized rear axles holes are the root cause of a lot of the hopping problems on the JLTOs since the rear axle assembly is able to move up/down and forward/back at will and the JL motor/magnet combo has very good torque.
Your best bet is to start out with a chassis that doesn't have a lot of slop in the rear axle before embarking on the upgrade path with the other components. This involves picking through your inventory of chassis parts from the 7 releases and mixing, matching, and swapping around parts to build that "one best car" from everything you've got. If you're going to be racing these cars competitively you can't be concerned about keeping all the parts that came with a particular car together. Parts is parts. You also can't assume that any random combination of parts (which is what you get out of the box) is going to get you what you need. Before spending the time and money building up a car for racing try to start with the best of what you've got in box-stock form and go from there. Try different combinations and test, test, test, and test. You can repeat the parts selection and test process for however many "race ready" cars you want to build up. You'll ultimately end up with a small number of box stock cars worth investing more time and money into with those expensive aftermarket hop up parts. You'll also end with a bunch of decent runners that just need silicone rear tires to be fun to drive but maybe have a few little quirks or are lacking in some way. You'll also end up with a few dogs that work well for mounting pretty bodies that you don't run on the track.