I've seen one in the rough; we had one as a safety boat for the Scorpion Nationals in 2004. We had up to 5ft of swell that week, and we tend to get steep, short stuff. As far as I remember, it handled it well enough to last all week. The crew got a hernia, but whether that was crashing through the waves or handling marks and anchors I'm not sure — I think they were responsible for the holding marks off the leeward end of the course.
But it was ten years ago, and I didn't get to try it myself. Given the difference (huge) between an SR4 and a Ribcraft 4.8 in the rough, I'd not like to speculate on the difference between an RC3.5 and an SR4.
That said, a six or seven hour day in an SR4 can be pretty wearing when it's up in heaps, and the boat will easily outlast the crew. I imagine it's much of a muchness for most small boats.