Overload/underload training with the super speed slugger

Sorry if this sounds blunt, but it sounds like you have $300 that's burning a hole in your pocket.  I think training with a heavy bat is fine but this can be done with simple weights that aren't very expensive. And you can add weight as you go.  Regarding the radar, exit velo is what you should be looking at and a more flexible radar gun (or pocket radar) can be used for this.  I guess I'm not a fan of expensive gimmicky things.

Total scam, same thing can be done yourself for "pennies"

Each penny weighs 0.088 ounces

Buy the shortest fungo and a normal bat (the cheap $30 Louisville's are perfect

If possible, weigh them, otherwise the listed weight is close enough

Calculate how many pennies you will need to make each bat desired weight

Fill an old sock with pennies, even them out and tape the sock to the mid portion of the bat

Plenty of plans available online, I know the super speed recommends players swing from non dominant side as well as dominant side (righties swinging lefty in addition to right handed swings)

Good luck and I hope I saved you 260 dollars

I like the pennies idea. My kid has a -20% to +20% bats. I guess I could just modify them to the -20/-10 & +5% and follow their free plan. I already have a pocket radar and zepp so the speed radar is redundant tech. The money in the pocket is quite warm. 

I vote gimmick.  In hitting you want to know exit speed and launch angle.  That's it.  If you are getting lessons and those things aren't improving, run, run fast.

Get an old "senior league" bat cheap from eBay (holds up hitting better than a fungo) and tape pennies to a wood bat or drill holes and put fishing sinkers in it.

I drilled a hole in the end cap of old BBCOR and shot about a 1/2 pound of cheap caulk into the barrel.  The caulk doesn't rattle or shift around.