Double cab bed extender for dirt bikes

I'm getting a double cab soon, mainly for hauling dirt bikes. My bike is almost out of the bed with supermoto wheels on, and will be even further out with knobbies on.
I'm interested in the Ready Ramp since I will need a bed extender to keep the rest of the gear in the bed, and it will double as a moto ramp. I also like that it is square, not rounded like the Toyota bed extender, so it maximizes space. But I'm not sure if it will be long enough for a longer bike with knobbies.
Here's a pic of my supermoto in the bed, but not pushed all the way forward. With the knobbies on, it will be longer. I could save some room by tying it down diagonally, but when hauling more than one bike, they will need to be more or less straight.

I might need to get something like the AMP Research Moto X-Tender, but it will not double as a ramp.