First of all, what wind force are we talking about ?
I can't say anything about the Severne sails, because I've never used them.
I'm using a Gunsails MegaXR 10.9 on the US147 and find it a perfect match.
It works fine and comfortable between 8-12 knots average and peaks to +/- 15 knots.
Much easier than on my F161, but the F161 points better and is faster upwind
What you describe reminds me a bit of my old Gunsails 9.5 freerace sail that I used on my F161.
It was a very early planing sail but I always got so quickly overpowered with it, when the wind picked up.
The Mega XR 10.9 is a lot bigger and heavier, but much more stable and easier to control in the same wind conditions.
Again, I'm not sure if the difference is the same between the full race and freerace sails of Severne, but if you get the chance to test a reflex, I would not hesitate. A friend told me that the reflex sails cover an extremely huge wind range.
IS87 / IS101 / RRD114 / US147