During initial construction I managed to JB-Weld the motor retainer backwards (even after double-checking).  Discarded original 36" tube and replaced with 48" tube and 54mm threaded slimline retainer.

Initial rocket length: 83.5"

First flight (2014-09-13, I215) resulted in ~1.5" zipper on lower BT due to ascent separation.  BT cut 1.5" shorter.  Renamed "Bumbl-B mk II".

mk II rocket length: 82"

Second flight (first as mk II, 2014-09-13, I65W-P) resulted in ~1" zipper on upper BT and ~15" zipper on lower BT due to failed drogue charge (bad e-match).  Cut upper BT 1.25" shorter and lower BT another 15" shorter.  Renamed "Bumbl-B mk III".

Lower BT had to be cut below the original hardpoint anchor as zipper ran down to the hardpoint.  Replaced with Aero Pack M54E retainer (drilling 5 holes for motor ejection bypass).  Upper and lower BTs epoxied together at coupler (no longer separates).  No longer capable of carrying electronics other than inside nose cone.

mk III rocket length: 65.75"

Thirteenth flight (tenth as mk III, 2015-03-21, I245G-12) resulted in 2.6" zipper on lower BT due to late AT motor eject.  BT cut 2.6" shorter.  Renamed "Bumbl-B mk IV".

mk IV rocket length: 63.125"

Fourteenth flight (first as mk IV, 2015-04-04, I357T-12) resulted in significant airframe damage due to very early AT motor eject.  Lower BT zippered down to coupler from mkIII repair.  Additionally the Slimline motor retainer was crimped during landing, had to be hacksawed off rocket.  Rocket finally rebuilt March 2016, with two new airframe sections and new avionics bay coupler to replace damaged piece and restore original dual-deploy design.  AeroPack M54E used to replace original Supermount during mk III repair now used for motor retention.   Renamed "Bumbl-B mk V", used name "Return of Bumbl-B" on first flight card but name was not announced.

mk V rocket length: 82"

Fifteenth flight (first as mk V, 2016-04-02, I225FJ-P) resulted in ~18" zipper of lower BT due to failed apogee chute deployment (36" chute stuck in airframe).  New BT section zippered entire length, down to coupler from mk III and mk V repairs.  Rocket is awaiting rebuild once again (mk VI).