MT/FZ07 is a great bike. If the insurance company only cares about the displacement, neither this nor the SV650 solves the problem, though.
There are some other new choices in the smaller displacement class that aren't "bigger" than the RC390 but could potentially be "better" in other ways and have a more upright riding position: Yamaha MT03 (essentially a naked higher-handlebars R3) and Kawasaki Z400 (essentially a naked higher-handlebars Ninja 400). I haven't ridden a NInja 400 but I have an R3, and it is quite a bit smoother-running than an RC390 ...
There are some other new choices in the smaller displacement class that aren't "bigger" than the RC390 but could potentially be "better" in other ways and have a more upright riding position: Yamaha MT03 (essentially a naked higher-handlebars R3) and Kawasaki Z400 (essentially a naked higher-handlebars Ninja 400). I haven't ridden a NInja 400 but I have an R3, and it is quite a bit smoother-running than an RC390 ...