Exactly - replacing with a 7L will be like putting the standard small carb on the 3000, using the 7D will be like putting the BIG ST4500 carb on it.

And just as a test, you might dilute your standard fuel with methanol so its about 10-12% oil - use a hotter plug/colder plug.

I've used the OS and ASP carbs as well as the ST4500 carb - all work ok if you take some time, just start with the high adjust, then do the low needle, then back and forth high to low a couple of times. Run it smoking rich for the first flights and see if they last the whole flights, then dial it in a quarter turn a flight till you're running ok with smoke showing once in a while.

I also put a constant glow system on mine, keeps the plug hot all the time and I haven't had an engine go out since I put it on. Just a pair of wires off a four cell, c-sized battery pack with a cut off switch on it.