Some hybrids might be fussy, but most can be drastically cut back.

The rule of thumb is that you can cut about 1/3 of the leaf area off at one time. In actual practice some people cut them back to a stump. It the plant is healthy, it will usually come back in either case. If it is in too much shade, it will come back a little spindly anyway. They need some sun to keep their shape and bloom. Prune immediately after the blooms drop to give it the most time to grow and form next years flower buds.

Thanks rhodyman, this Rhodo was in too much shade, I moved it a year ago. It likes this location a lot better, seems healthy and will bloom this year but was thinking of sacrificing the blooms to give it more time to send out new growth. The only thing that is wrong with it is it's really leggy. I'm more concerned with getting a nicely shaped shrub than the flowering aspect at this time.

A......

If it didn't burn up last summer apparently the change in location isn't bothering it enough to be concerned about cutting it back heavily. However, there is still the matter of the root zone heating up if the whole top is cleared away all at once.

Bboy has a good point. That is why a good mulch is important to help keep the root zone cool. I seldom prune, but when I do prune, frequently any new leaves that are left get severely burned since they were adapted to being in the shade. This too will pass ;) If you prune before they bloom, you will avoid this problem, but you will loose the flowers.