How high should you run clam shell isobaric woofers?

[Greggo]

Just wondering if anyone has any experience or well formed opinions regarding crossover limits when running woofers isobaric loaded in clam shell fashion, meaning that the rear of the driver faces into the room, so the basket and the magnet present a significant range of surfaces to mess with the cones freq/power response.

I know that Volt has "radial" drivers that place the basket in front of the cone and they rate these types of drivers up to 500hz and even 600 or 700 depending on the model. If I was going to design a three way speaker or line array and wanted to minimize distortion to the maximum extent possible by picking low distortion drivers and then loading them together clam-shell style to cancel distortion artifacts even further (and theoretically have them behave in a more linear fashion across the board), would you be comfortable running them out to 250hz, 500hz, maybe in an extreme case even out to 750hz?

I am thinking about something like a seas or adire extremis, both known for good open basket and magnet design to get out of the way of the cone as much as possible. I suppose a woofer cross over point between 90 and 150hz would be no problem, but what if I wanted to hand off to a mid dome at around 650-750hz with high slope digital crossover, do you think the range from 500-1000hz would be heavily compromised by having the driver firing backwards into the room, even with a digital crossover set with a 48db/octave slope or higher at around 700hz? Please share your thoughts?

Thanks,

Greggo