I have not had any heat related issues with my R-4 Pro, Jim, and have used it in some very heat-intense situations.
I think if you need something that is going to sound good stock, the P2 is going to be better than the R-4/R-4 Pro. However, a Busman Mod. R-4 Pro through Cascademedia is no more expensive than the MSRP and I'm sure the regular R-4, as well as both with the Oade Mod offerings, will also be not much (if) more than a stock unit purchased new. Some used R-4s have been floating around the YS lately.
I knew I wanted a 4 track HD unit, and I agonized a bit over the R-4 vs. the R-4 Pro since a SD 744t was way more than I could possibly afford. The AES/EBU digi in (w/o resample) on the R-4 Pro vs. a s/pdif in on the R-4 (which does resample), in combination with the gain/trim pots (R-4 Pro) vs. line/mic in switch + gain pot (R-4), convinced me it was worth the extra scratch to pony up for the Pro.