I got kinda intentionally stuck out in a thunderstorm last week...60 mph winds and nearly 2 inches of rain in 30 min with some quarter-sized hail. I wanted to see what would happen and how the boat (R21 Classic) would perform in these conditions. Keep in mind that this is on a 3,000 acre lake with a max 2-mile fetch and lots of places to quickly hide out.
On the extreme downwind side of the lake, after about 20 min or so of 40-60 mph winds across a nearly 2-mile fetch, the waves were large and square and visibility was nil - 50 feet or so in the rain and hail. I took a foot or so of solid water over the bow many times. Reversing into these waves just to see what would happen, I never took solid water over the stern, but as you can imagine, there was a lot of hammering and very heavy spray. Beam-to the waves, Nellie May really rocked and rolled, but never too any solid water over the rail...lost of heavy spray, but nothing solid, even with breaking waves. The bilge pump ran pretty much continuously.
I had the door open pretty much all the time (except for the reversing), and kept an eye on the cockpit. There was never any water that accumulated more than an inch or so, and that was mostly from the very heavy spray while reversing into the waves. While going forward, the drains completely handled the spray, even whilst taking solid water over the bow.
Admittedly, this was on an inland lake, and does not come close to oceanic conditions. That being said, very close, steep waves of 3 feet or more present a pretty good test. Heading into the waves at a slight angle was the most comfortable and driest, as that tended to lengthen the effective distance between crests.
I had my GoPro set up and running. When I got home after the storm, I found that in the excitement, I left the lens cap on <frown>.
These R21's are pretty capable little boats, and I do not think the lack of self-bailing is a real problem. The cockpit is so large and even with pretty large scuppers, a boarding sea would probably be the end of it, and the conditions necessary for that to happen would probably be pretty severe.