[notmytarga]

The drawing looks like the propeller will hit the wire....unlikely, but certainly a problem if it did.

Bringing over principles from the Pinewood derby, where we have achieved some , cough, cough, success .... Air resistance is minimal at this scale although because the propeller provides thrust any protrusions would obstruct the flow.

It will be easier than Pinewood to set up a test race. The weight of the rocket will likely have a sweet spot - I would optimize this. Since it self-acclerates lightness is helpful for starting and having less friction on the hanger, BUT - if the rubberband power runs out before the end you will want some mass to maintain momentum. The critical item is friction and alignment aqnd fore and aft position (balance) of the hanger tube - there are likely rule limitations to modifying the hanger with bearings etc - ceramic would work well if allowed. Make sure that the dynamic axis of movement does not cause even slight binding in the tube. The rotational and off-axis thrust forces make this a dynamic/kinetic situation. A tail fin/rudder could help with that.

I found that with the Pinewood Derby, Rain Gutter Regatta and likely this activity that alignment to minimize friction losses is what puts boys on the podium.

Test, test and good luck.