Hah, thanks for the reply, but seems I might have been getting ahead of myself. I was used to reading the original Intel "bible" which can be a bit dry reading at times. In going over the datasheet for the Philips 87C51 (to look for those temperature vs voltage specs) I ran across the discussion of using the timers to generate baud rates (on page 10), and using timer 2 allows for much finer control of higher baud rates, so it seems like there is no need for things like overclocking afterall.

Thanks anyways for the reply which sent me back to that datasheet :-)