Well now I carry 4 see pic below.
1) Smaller Simms box has dry flies and attractor patterns such as stimmy's , Trudes, coachman. Also some San Juan worms, woven stonefly patterns...general big uglies
2) bigger Simms box carries big nymphs such as all my hares ears, prince nymphs, franks flashy, tungsten surveyors etc etc. obviously has empty space, will put in some small streamers and tie more of the above. My collection thinned out last spring/summer
3) thin box#1 has all my beadless midges, disco's rs2, jujubee, mole flies etc etc
4) thin box #2 has all my bead head midges...rainbow warriors, zebras, two-bits, calico midges etc etc
The I shown 5th box I rarely carry has all massive salmon fly imitations, sizes 2's thru 6's and streamers.beleive it or not all 4 of this fit real nicely in that new Simms pack so 4 boxes doesn't seem excessive anymore. I love those thin boxes for midges.