Sinar F2 has a ridiculous amount of rise. The Sinar Norma is nice if you want an even more stable camera which typically weighs only a pound more. Most Sinar system components are interchangeable.
Alan - I've often used a 450 C Fujinon on Sinars, and in fact generally have the camera set up with about 22 inches of rail. The cumulative weight and bulk are less than using an equivalent focal less telephoto lens, and the image circle is way bigger. It takes just a moment to either increase or decrease the length of rail sections.
Something as light as a Toho in combination with a long lens would seem to be vodoo with even the slightest breeze or jiggle. But the stability of any monorail camera system can be greatly improved by bolting the rail clamp directly to the top of the tripod platform, without any kind of intervening head. "Wobble-bobble" ball heads tend to be the worst. What sense does it make to find the lightest camera around, and then carry a bunch of redundant head weight? Double jeopardy.
When I need to travel lightweight with a 4x5, I reach for my little Ebony folder. My 8x10 is a Phillips folder. The Sinar monorails are faster to set up and operate, and more versatile in terms of focal length extremes.
What gets classifed as "lightweight" is all relative. I've backpacked tens of thousands of miles with Sinar gear, along with full mountain gear and supplies, typically around an 85lb load. Now at 75, I'm looking for the camera with the biggest bellows I can find, so I can fill it with helium ! Balloon travel is getting tempting.