I'm with pdmoylan. A view camera isn't the right tool for photographing mobile subjects at relatively high magnification. Especially in "the field."
I took up photography with the goal of shooting unconstrained fish in aquaria. This is nearly your problem, David. In 1971 the best tool for that job was a 35 mm SLR with a macro lens. Hand held, focused by moving the camera/lens to track the subject. A major part of that art is arranging the tank so the fish does what the photographer wants to record where the recording is easy.
The techniques I developed for shooting fish transferred directly to shooting flowers and insects at low magnification -- the highest my usual rig allows is 0.88:1 and shooting that high handheld isn't easy, focus is too easy to lose -- in the field. Multiple flash units attached to the camera body or the lens' filter threads, calibrated so that I know which aperture to use given magnification and flash power settings. No thinking required, just consult the tables, set up, compose, focus, push the button.
The ancients used focusing frames with non-SLRs to work more rapidly closeup. Most often fixed focus cameras with a + diopter. For an explanation, see Gibson, H. Lou. Close-Up Photography and Photomacrography. 1970. Publication N-16. Eastman Kodak Co. Rochester, NY. 98+95+6 pp. The two sections were published separately as Kodak Publications N-12A and N-12B respectively. Republished in 1977 with changes and without the 6 page analytic supplement, which was published separately as Kodak Publication N-15. 1977 edition is ISBN 0-87985-206-2. Focusing frames are discussed in the Close-up section, -A.
I've tried to make a couple of focusing frames for shooting flowers with a handheld 2x3 Graphic and electronic flash, haven't yet come up with a design I'm willing to build and try to use. Haven't come up with a good set up procedure either, and am not sure I can see exactly where the plane of best focus will be.
So you'll know and perhaps reconsider, I have a set of good lenses made for shooting above 1:1 and the adapters needed to mount them on a Nikon, have tried working at 5:1 handheld. Luminars, Minolta Compact Bellows with strings of adapters, supplemental tubes as needed, ... Short answer, don't bother. Keeping focus is very difficult. Perhaps with digital where the incremental shot is free and with a sufficiently powerful repeating flash. But not with my gear.
pdmoylan's remark about separate flashes for the backgrounds is great. That's the only way to control the background's lighting; flash(es) mounted on camera and lens usually make a black background.
David, before you proceed further have your sanity checked. You want to shoot a 2.5 mm insect and get a 95 mm image. Fine, wonderful, but that's 38:1. 38:1 requires 39 * f extension. You haven't thought about what that means for the 120 mm lens that doesn't appeal to you. You're nuts or extremely clueless.