Having had the standard length Berlingo (same as Rifter) and the “Long” Rifter I can say with some certainty that you would have to drop the seats in the standard version to get everything to fit.
I’m actually looking at trading my C4 Grand Picasso in for another Rifter Long GT Line at the mo, it absolutely monsters the Picasso on boot size and that’s a larger boot than the standard Rifter.