I'm debating the same thing... I think I would have more fun on the DRZ, but I much prefer drier trails in July than deep greasy mud pits in April.
Corpse... basically the Bethany is two rides in one. The big bike track does a gravel route and a few no-maintenance road allowances and the most you'll run into is a slight mud puddle or a bit of sand. If it is like the run I followed with Supernam last fall, you could likely do it with mostly street tires.
The dirt track goes into the Ganny, but I think it occasionally hits a road or two, so I am not sure if your CR250 would meet the licensing requirements. Once ODSC has the details finalized, I'll post up whatever they present.
Can you post the PDF? Can't see it if you're not a member.
I82l8, the big bike route is mostly gravel roads and maybe a bit of pavement.
I don't remember the water being that deep 2 years ago, when I went. How was it last year?