When to step up from 3.000 to 3.250 axle tubes
 

My mini-tub is mid way through completion, so attention is turning to which axle housing/tubes to run.

I'm wondering at what point is the extra stiffness of 3.250 axle tubes deemed beneficial? Initially the car will be around 500rwhp, but given the $$ investment in the rear end I want to future proof it for FI upgrades down the track, with of a power ceiling of around 8-900rwhp. It will see some DR's and some (hopefully!) low 60' times, and go around corners too!

The proposed unit is based on the Strange H1114 unit, which will be braced not by a traditional back brace, but with additional stiffness provided by watts link link mounts (see img)

Will be running floating hubs, Strange S Trac centre and 35 spline axles, so I've already made one or two calls which will increase weight in favour of durability, so I'm wondering if I should go ahead with the big tubes as well and make it a tank, or at that power level will 3.00 do it easy enough?

I've been planning a similar axle set up and have wondered the same thing.