Hi,
I have noticed cameraViewport framing works only in case Render TOP has geometries specified as constant parameter value. This is due to line 258:
geoOps = renderOp.parent().ops( renderOp.par.geometry.val );
Since in current versions is geometry parameter properly evaluated to list of operators, I believe it would be better to change this line like this (it will be faster and also it will support other parameter modes):
geoOps = renderOp.par.geometry.eval();