I have tried to sit in a SPF more than once, just can not fit comfortably. They seem to like people that are 5 foot 9 inches and too bad if you are taller.
I was able to sit in a CAV. It seemed fine, but I did not have a brain bucket on at the time.
I asked SPF if they had any plans to accomodate a 6 foot plus tall person and they said "other than a Gurney bubble, no."
No SPFs for me, I'd take the CAV.
Just my experience with this.
