Good morning;
An interesting question. I have just purchased my first dedicated photography backpack; a Lowe-Pro Compu-Trekker Plus AW. I have no idea how it is going to work. I have just begun to see how things fit into it. I have tried it on to see how it fits, but I am not really sure about that part yet. My logic for getting it was for the ability to carry a laptop computer in relative safety. We will see.
For the 4 by 5 SINAR F1, I have been breaking it down, folding it, wrapping it, and putting it into an old Kelty Redwing internal frame backpack when going out a short distance to get to the scene. If I am working alongside of the road, I just put the SINAR case in the back of the Subaru. If I am going further, then the SINAR goes into a Gregory Shasta internal frame backpack along with the "ten essentials" and other things if I wind up being out longer than I anticipate.
The 2.25 Square gear or the 35mm gear can go into whatever pack seems appropriate for the distance and time involved.
For mountain topping with the small radios, I put everything into a Gregory Denali Pro expedition size internal frame backpack. This includes the tent, sleeping bag and pad, a small solar panel, and other things, along with usually a Minolta X-700 35mm camera and a couple of lenses. I have tried to carry much more in the past, but this excessive accumulation of years is starting to get through to me, and while the Denali may have a lot of space (it really does fit the antenna system inside the pack), I am trying to keep the weight down to something manageable.
Enjoy;
Ralph
Latte Land, Washington