Anything 4" (BT101) flown on less than a full 40n-sec E motor is a worthless flight in my book.
Like trying to fly a Mars Lander on a B4-2.
Makes zero sense.

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When in doubt, WHACK the GAS and DITCH the brake !!!

Yes, there is such a thing as NORMAL, if you have to ask what is "NORMAL" , you probably aren't !
Failure may not be an OPTION, but it is ALWAYS a POSSIBILITY.
ALL systems are GO for MAYHEM, CHAOS, TURMOIL, FIASCOS, and HAVOC !

Repairs over the years has pushed mine to 17 oz, it flies nicely on an E28 or F35. The new Q-Jet F41 might work too, but not sure I'd trust a single-use in this vintage bird. And has kind of a weird progressive thrust curve.

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Paul
If we weren't all crazy, we would go insane - Jimmy Buffett
NAR #87246 www.wooshrocketry.org

The Boyce 4" Pershing comes with a 29mm mount.
Mine is so heavy, I doubt it would get more than a few feet off the pad even with a 40n-sec E.
Granted, if built for a 24mm E, it wouldn't need all that nose weight, but the ballast isn't coming out now