Yeah my stroke rate is a bit higher too.
In the boat I was at 36 for the weekend but I'm generally 38-40 on the erghttps://ar.attackpoint.org/sessiondata.jsp?session...
I find the resistance is not as much as the water but you are getting no respite on the recovery arm so its constant work.
Great that you are getting a feel for it. It is pretty close to the action on teh water so no harm in a couple of hours a week on it