Good suggestions - thanks.
Of course, that's why I asked here, where the creative juices run freely; like coolant dripping down your arm to your elbow.
I'm still having trouble conceptualizing fitting an engine into the space of a basketball; but it's a personal problem - no worries.
As an aside, an engineer purportedly developed a rotary engine which is almost like a reversed Wankel design.
The design has the rotor in the shape of the two lobes of the epitrochoidal curve, inside a container where the _inside_ surface is in the shape of the _outside_ of the Wankel-design rotor (the bulging equilateral triangle), the container now functioning as the "block".
Apparently this allows 3(!!!!) combustion chambers instead of just one like in the Wankel design.
Presumably that solves the low torque issue of the rotary engine.
Now THAT'S thinking outside the box.
I'll see if I can find a link and add it here...