Which engine....
"Disappointed in the long run" with the .70FS?
Get out....
I've owned .70's for 15 years and am eagerly awaiting my first disappointment. It's not happened in all this time, but I feel better now that I know my first class ticket to "Sad City" is in the mail.
The .70 is a fabulous engine. Easy to run, and maintain.
More than enough power with a 13-7 for the Big Stick using 10% nitro fuel.
If all you want to do is "go vertical"....then buy an estes rocket.
'Race