I have 2 of these as well. A few thoughts, in no order.

If it's quitting, it's almost always because it's lean. This can be on take off as you describe, or most any other times. Sometimes, figuring out why it's lean can be a real challenge (e.g. hard to see cracked/disconnected/melted muffler pressure line)

I was getting pretty good at dead stick landings/getting a lot of practice with one of mine, until somebody mentioned the fuel nipple on the carb has a gasket underneath it, and his had partially disintegrated. Mine were just loose (both of them!), leading to a dead stick when I pulled back on the throttle (over and over and over again).

I found the adjustment procedure in the owners manual very well written, and despite the fact I've been screwing with 2 stroke engines for a long time, these procedures were just different enough where I have to go back and reread on occasion. Not hard, just different.

You might want to step up to a 12x6 prop if your 11x6 has been run a while. The lower rpm it will run at might make it a little easier/friendly when it comes to proper tune. You might like how much quieter it is too.

Best of luck, hope one of these thoughts will lend a hand. -Al