Not a sim expert. I noticed the configuration
" [no motors]"
If it means what I think it means, gonna be a problem when motors added.
May be "tweakable" however with the fins a bit bigger, the body a bit longer, and the motor mount a bit longer (fins further back) without losing too much "Loony Tunes" (? "Luny Tunes"?) flavor.
Those pointy fin tips may be a bit breakable.
With that small motor mount and the BIG body tube, this would be a NICE model for rear ejection. You got TONS of space for chute between the mount and the body.
The nose cone is glued (and I mean REALLY SOLIDYLY glued) in place, the motor mount is extended all the way up into the nose cone (put something in the inside of the nose cone tip to protect it from the ejection blast, or PLUG the forward end of the motor mount and punch a bunch of side holes to let the ejection charge go out the sides of the mount, still works.) You need a forward centering ring placed just aft of the base of the nose cone.
Beauty of this is, you can put weight/mass on the forward end of the motor mount which is actually inside the interior of the nose cone at launch. With rear eject, the rocket comes back in two parts (you can connect them and use one chute or let them separate each with it's own chute.) The fin/motor mount unit with fall NOSE end first, so the weighted forward end of this unit takes the impact when it hits the ground, not the fin tips. Meanwhile, the rocket BODY and NOSE CONE section is a much lighter, so the impact has less force on it as well.