Always remember there are TWO films labeled as Tri-X, apparently intended to confuse the market (and BOTH are available in 120!). Small-format Tri-X, aka Tri-X Pan, TX, or 400TX, is ISO 400 and Diafine lists it at EI 1600; a lot of users prefer to rate it at 1000 to 1250 for Diafine in order to gain shadow detail. Large-format Tri-X, aka Tri-X Professional, TXT, TXP, or 320TXP, is ISO 320, listed at EI 1000 on the Diafine box, and while I haven't tried it in Diafine, is likely to garner a similar discount with the shadow detail fanatics.
My daylight tubes are pretty simple, really. For 4x5, I use a five inch length of 1 1/2 inch black ABS drain pipe (though you could probably use gray PVC, white PVC is too translucent and will surely fog the film). I cut the pipe in a miter box with a handsaw, but a plastic pipe cutter, power miter saw, or bandsaw with miter gauge will do nicely as well; you want the cut as square as possible, and once cut, you'll want to smooth the cut end, chamfer and deburr the inside on both ends with a small sharp knife (just skive off a little shaving all the way around to chamfer and deburr, after sanding or trimming any irregularities). On one end is a plain cap of the same material; I don't glue it, just friction fit it in place (for easier cleaning). On the other end is the light tight filler cap.
The filler cap is another black ABS cap -- this one must be the type with a sort of "chamber", that is, a cap deeper than the gluing socket by about a half inch, since you'll need the extra depth to install the light baffle. The baffle can be made from another cap, if you're only making a few tubes, but I made mine from 1/8" black ABS sheet, textured on one side (the 3/32" didn't seem opaque enough). The sheet is cut to a square with diagonal the same as the outside of the pipe, then the corners trimmed until it will enter the chamber of the cap past the gluing socket -- but don't glue it in yet.
Drill a centered hole in the cap and ream or scrape to a close fit on a piece of 1/2" gray PVC (can't get ABS that small) about 2 inches long. Glue the PVC into the hole in the cap with "transition cement", made specifically for gluing PVC pipe to ABS pipe -- put the inner end of the PVC flush with the inside of the ABS cap. Now install the light baffle (I put the textured side toward the filler, to reduce specular reflections) and fix it in place with drops of regular ABS pipe cement. Use a PVC pipe cap on the filler tube as an inversion cap.
Load by curling the film, emulsion side in, and slipping into the tube; the stiffness of the film base will hold it open so chemicals can get to it. You will often find the antihalation dye doesn't completely wash out of the base where it contacts the tube wall, but a couple minutes in hypo clearing agent or a solution of 2% sodium sulfite with 1 tsp per quart of sodium carbonate will remove the remaining dye; I just routinely soak in this solution after fixing and before washing the film, as alkalizing the gelatin also speeds washing. Scratching isn't a problem -- I have negatives with scratches, but they're all parallel to the long side, from sliding the film in and out of film sheaths, not across the long dimension from sliding in and out of the tubes.
Do test your construction, but my tubes are light tight in full sunlight, at least 10-15 minutes exposure with ISO 100 film and the sun shining directly into the fill tube -- no fogging at all (I did have one sheet fog recently, developed to EI 3200 or 4000, but that one may have been hit by afterglow from a fluorescent lamp in the bathroom I use as a darkroom; others at that EI were unaffected). The baffle has enough open space around it to fill and drain rapidly, and if I need to I can use a second piece of tube and a union to double the capacity of the tube -- I have three of these, with two tube sections each, and can thus load six sheets at once. For 4x5, each tube wants about 8 ounces of liquid; for 9x12 cm, the sheet can be curled with the long way around the tube instead of short way, and thus can be as little as 3 1/2 inches long; this needs only about 6 ounces of liquid.
Sorry, I keep forgetting to take picures -- perhaps I'll get the digital and do that today.
Oh, yeah -- because I fill the tubes completely with developer, I can use intermittent agitation and "small tank" times, same as when I develop roll film in stainless or plastic tanks with spiral reels, which also means I can use agitation to control contrast as I do with smaller formats. I use very dilute developer; I'd recommend that, because these tanks aren't very efficient relative to the film area. If developer economy is a major issue, you could make up a PVC core that could be glued to the inside of the non-filler cap that would pretty easily reduce the capacity of the tank by 50%. With HC-110 Dilution G, you need a minimum of three ounces of liquid per 4x5 sheet anyway, so there's little point in trying for a closer fit of core in tank; I haven't bothered (developer is cheap enough, and I don't shoot a huge volume of large format).