Hello
More fun with the JB weld!
I have been converting RC engines into C/L for a while now using wooden dowels, alloy tube, glue bottle tops and JB Weld in fact I have converted many for combat hacks just to get more models in the air for my boys to fly (or demo!). Glue bottle tops cut off at the right opening size then glued into a appropriate sized alloy tube give infinite choice of venturi size and can be blended in with JB weld for a smooth contour. A wooden dowel replacing an RC throttle barrel can be drilled to the desired size and a tube or N/V assembly added.  Also use Tatone in cowl mufflers or cut down Du-Bro stacks on combat wings to cut the noise and satisfy rules regarding mufflers.

Regards Gerald