Brief:
I added a booster with gap stagin' for me stock Fat Boy.

Modifications:
T' Fat Boy was built stock. Ahoy! Begad!

For t' Booster, arrr, t' engine mount be assembled in t' usual manner. Well, blow me down! Blimey! T' aft centerin' rin' is flush with the tube end. Aye aye! Blimey! 1/4" vent holes were punched in both centerin' rings. Blimey! Blimey! Avast! Blimey! T' coupler extends into t' sustainer approximately 1/2" with a pretty snug fit. T' fin pattern was upscaled a bit (the root o' t' fins measures at 3 3/4"). T' fins are surface mounted and cut from 1/8" balsa. Ya scallywag! Blimey! Avast! Blimey! A separate launch lug be added t' t' booster to give a little extra guidance.

Construction:
T' parts list:

• One Fat Boy kit
• 5" o' BT-80
• 1" BT 80 coupler
• 2.75" BT-20
• 2 80-20 centerin' rings
• 1/8" launch lug
• 18mm engine block
• 2.75" engine hook
• 1/8" balsa stock

There are absolutely no "gotchas" in buildin' t' Fat Boy itself. Begad! It is a well known kit after all. Begad! The booster was no more difficult t' build than t' original kit. Begad! T' Booster is pretty stoutly built. Blimey! I considered using TTW fins, me hearties, but given t' tumble recovery o' a booster, me hearties, I think it is much better t' pop a fin on landin' than break it.

Finishing:
Finishin' and paintin' went pretty smoothly. Blimey! Ahoy! Blimey! I decided against usin' t' supplied decals as I have this thin' about stickers. Instead I went with a simple yet dramatic paint scheme.

Flight and Recovery:
First flight was t' single stage Fat Boy on a C6-3. Avast, me proud beauty! Nice straight flight and clean recovery on a 14" nylon chute. Begad! Aye aye!

Second flight used t' booster with a C6-0 t' B6-6 combination. Arrr! Boost was slow and straight, matey, stagin' occurred fairly low and t' sustainer took o' like a shot. Avast, me proud beauty! It weathercocked a bit but had a very nice high flight. Begad! Chute ejection was a bit past apogee but deployed cleanly. T' booster popped a fin loose on landing, which be easily repaired. Begad! Aye aye! T' sustainer made a clean landing.

Third flight used a C6-0 t' B6-4 combination which gave an almost identical flight t' #2. Ejection occured at apogee and both booster and sustainer returned without damage.

Summary:
T' Fat Boy by itself is a fun little rocket, matey, which is suitable t' all kinds o' modification. Avast! I was worried that the addition o' a booster would make it t' heavy t' fly on an 18mm engine, shiver me timbers, but it works very well. I certainly wouldn't use any booster but t' C6-0 though. Aye aye! For a small field stagin' demo, I think it's just perfect.

PROs: It's a two stage bird that you don't have t' chase all over t' country side. Begad! T' gap stagin' has worked flawlessly so far. Begad! Ya scallywag! Easy t' build and modify.

CONs: I would like t' have seen 1/8" balsa fins used on t' stock Fat Boy. Aye aye! Sticker decals. Ya scallywag! Blech!