Time Trial / Time Trialling / TT

Spent an hour on the turbo this evening, turning over my legs & pretending I was doing real exercise, but really just getting used to spending an extended time in an aero tuck (without falling off).
Will I just need to HTFU and get used to weight-bearing on my shoulders?

I'm pretty sure I 'bear more weight' than you and I rode 24hr on aerobars actually pretty comfortably. It wasn't as aggressive as my 25/50/100mi setup but still aero.
You'll get used to it after a couple of rides. If this is new to you, you'll probably change your position anyway.