You asked about speeds and the truth is that it is not hard to drive these boats at 6 kts even in breezes of only 6 kts. You are not going to push her above 6.5 without some extreme effort.
The 23.5, 26 and 260 are all water ballast boats with a large main that is the primary driver of the boat. These boats sail best when sailed
FLAT. It is a very different feel than a traditional keel boat. So you need to reef early to keep them on their feet if you want to make good speed.
At 10 Kts, you will already have a reef in place. I always leave the dock with one reef in and shake it out if needed. If you don't have a second reef point, you will be sailing on jib only at 15 kts and maybe even have a few turns on the roller furller.
If you are going to regularly encounter 20 kts winds, you will def. want a second set of reef points in your main so you can keep your balance.
Spending some time getting your reefing system dialed in so you can reef and shake-out with ease will make your experience much better. I added three additional deck organizers and rope clutches to my H26 so that I could run ALL lines (including reef lines) to the cockpit.