I have a 2/2 twill scarf on my loom using Bambu 7 and have the sett at 16. I was inspired by a photo of a scarlet macaw from our recent trip to South America, and am using some pretty strong colours: my stripes are china red, apache blue, lime grass (in that order) with zingers of ginger and watermelon as I had bits of those. I wove a sample of 8 inches in china red using the twill draft as written in the pattern but feel that the diagonal stripe is too obvious. SO, I have been playing with various other treadlings, first on my Fibreworks and now on the loom. If I weave with the same china red, there is one prominent stripe. I think that my question is, should I be weaving with the same Bambu 7 in red or another colour (tried forget-me-not but wondering about a darker or lighter red), or another weight/sheen? Using the Handweavers Pattern Directory I tried a mixed twill: 1, 2, 3, 4, 1-2, 2-3, 3-4, 4-1 (the middle one pg 38) which really does look like feathers with the threading. A second one, on page 39, top, also looks ok but I am concerned about the floats. Any advice would be helpful.
If you want to keep all the colours bright and undiluted from the weft, you could increase the sett to around 20 epi and then decrease the size of your weft. I would use the 12 gauge bamboo and you will have a predominantly warp-faced scarf. You would weave it in plain weave. We do this a lot with chenille. You get the drape you want because the weft is so fine and your colours are strong and clear.
If you want to keep the sett the same and get rid of the diagonal line you could try treadling it in a broken twill fashion. Your tie-up would be 12, 23, 34, 41 but you would treadle them treadle 1, then 3, then 2, then 4. That will get rid of the diagonal line. As for the colour of the weft, it is difficult when you have such a contrast. One of the best ways to keep all those colours bright is to make your weft black. If you have any yarn in black, give it a try and see if that works for you. Your colours sound wonderful and I bet the red would be nice with the solid stripe on the one side. You could also add a 1/2″ stripe of the red on the other side and it would look like a nice asymmetrical detail. There are always so many options. Hope this is a little helpful.