Ive been wondering too. That is a really nice, classy product.
Have you contacted them? With you distance between sights they might be able to get you in the ballpark; or get the tallest replacement from H&R and maybe have to shorten for the distance you will mostly shoot and with the ammo you intend to use.
I think they give you the lowest height setting spec; you can mock up a wood, plastic, or alum. 'sight' for the back, tape it on and shoot to find the correction you need. The mock up doesnt need to be fancy, just a point of reference for center and at the right height for what you consider your close range. With that you can always dial in more elev. Some say to calc from the middle of the rear sight adjustment range so you can dial a bit either way to fine tune for ammo, etc. I use everything from CBs to HV 22s, rarely Hypervelo, so I would do some groups with all to see if I could find a happy medium.
