Yeah. I'd guess that Allen is a 4.70 guy as well. That sounds low, but plugging it into the Speed Score formula, that would be an NFL average time for his weight.
I'm worried that that is just too slow of a 40 time, regardless of the back's size. It seems like there's a threshold minimum for speed where even having jumbo size isn't able to compensate. To paint an extreme example, teams don't hand it off Fridge Perry style to huge guards that run a 5.2.
I don't know where that cut line is - how slow can you go? - but 4.7's got to be pushing it. Every NFL DB runs that, pretty much every starting LB runs that, and there are even DEs that run that. You can't get a step on anyone.
Maybe Allen drop some weight and gain speed, but as it stands, I think he's more of a fullback than a running back.