I bought one similar to Graeme's (different brand but look pretty similar... maybe made in the same factory!) and the wife has half constructed the insert. I used it the last few days on a photo trek (by car!) and once completed I think it will work great. I did actually wear it down to a waterfall and it sat nicely. Carring a wood tripod however is a chore, not to mention getting my unfit carcass up the side of a cliff (well it seemed that way) in 33C heat! I'll post a piccy once it's finished.
I too have a Kelty Redwing...I can say that it's a great pack. I only shoot MF. The internal frame is excellent and can be adjusted for a comfy fit. I usually carry couple lenses and backs. The tripod goes on one side (upright in the basket pocket) and I use the compression straps to hold it on. I can easily see doing an overnighter with this set up since there is so much room. The big bonus is a fill zip main compartment so you don't have to go in from the top of the bag all the time.
Graeme, What a great idea. I sported for a mini trekker. It fits all my LF stuff (crown graphic, two extra lenses, light meter, portable radio, notebook, dark cloth, film holders, & c.) but, it is not easy to arrage the internal foam padding in a satisfactory manner. These bags are obviously targeted to the 35mm and MF market.
I also bought a Kelty Redwing 3100 back in June 2004 (I posted this on a previous APUG thread). My 8x10 Wehman, 3 lenses, BlackJacket and filmholders, etc, all fit inside.
I received my Nature Trekker Backpack which I bought from Canada through eBay earlier this week. I have a 35mm based body (wink wink)70-200 2.8, 85, 17-40, 28-135, 28, 50mm lenses, a flash, meter, IR flash transmitter, filters, batteries, cleaning kits, etc all packed in it. And I still have two open slots! I see no problem using this with a 4x5 field camera with lenses and holders, there will be plenty of room.