I've done 12 days to Diamond in a 16' cat, and I'm an old geezer. So it can be done. And with this summer's presumed continued high flows, it would be very doable with appropriate boating skills.
Question is, what do you want out of the trip? This schedule will mean no layovers, and not many -- if any -- on-shore activities. But if you just want the pure on-river experience, yeah, it's well within limits.