Do not attempt to fly your shuttle without flame fins-- unless you want to replace your rocket with a smoking, balsa garnished crater...
The stack will NOT be stable without flame fins. Build the Flame fins according to the kit instructions (three fins, NOT two, spaced at the 9, 12, and 3 o-clock positions 90 degrees apart, NOT at the 12, 4 and 8 positions like a regular three fin rocket (120 degrees apart). Do not do like one lug nut I read about on an EMRR review who decided that the instructions were in error and that if the fins were 90 degrees apart it MUST require FOUR fins on each flame fin unit, which of course put two fins directly in line with the motor exhaust, which of course promptly burned them off in flight or charred them beyond all recognition... Then of course he complained about it like it was the kit's fault he was an idiot... LOL
The flame fins have actually been reduced in size somewhat from the original fin patterns that came with the early kits... back then they were a more "regular" looking clipped delta type fin. The "Flame" pattern was instituted and sized to still provide ample stability for the shuttle stack in flight while looking less obtrusive than the trapezoidal fins.
SO, in summation-- DO NOT attempt to fly a Zooch shuttle without the flame fins-- the rocket will be completely unstable and will spin out, part your hair, and crash in very short order. DO NOT attempt to modify the fin arrangement or reduce the number of fins or their 90 degree arrangement-- it will reduce the stability or cause the rocket to go unstable in flight, or could cause it to go unstable in flight, or fly in an erratic or unpredictable direction.
Unless you FULLY understand EXACTLY what the effects of any modifications you make will have on the stability of the stack (or are willing to risk your stack being destroyed, and are willing to fly in private alone to test your modifications to prove they're safe first) Of course the manufacturers recommendation is to build it PER THE INSTRUCTIONS...
Best of luck! OL JR