We had our R27-OB in 3-5 foot seas (with an occasional 6 footer) a week ago.
5 and 6 footers are quite tall. Worst sea state I've had to drive in.
Our problem was more about being able to see out the front (the windows fogged up something fierce). My wife would wipe off what she could reach on the port side, and I would do the same on the starboard side. Just so I could see the waves coming from both sides of the boat. It was a lot of water splashing and falling around us. Like driving through a waterfall, literally.
This was in Puget Sound, during a small craft advisory that called for 20-30kt winds, seas 3-5 foot. White caps everywhere.
Our tug handled it just fine. We were heading due South into a Southwest wind. So we were taking the waves nearly head on (at a slight angle, of course, as you would any oncoming waves). The boat rocked up and down, side to side as you would expect. Took us almost 2 hours to go 10 nautical miles in that mess doing 4-8kts. We weren't white knuckled or scared. We were dry and felt safe and secure. But we also felt like "I don't want to be here. Get me off this ride."
This was Friday.
On our return trip that Sunday, it was another small craft advisory, 2-4 foot seas. Same Southwest wind (15-25kts), except we were heading due North. At one point I felt the boat bogged down, I saw us doing 3000 RPM, 2.4mpg and 10mph. (On our boat, 3000 RPM should be like 0.8mpg). We were holding position on the uphill side of a wave that was moving 10mph.
The tug did great, we made it home safe and sound, and my wife still loves me.