undulating twill

I have been working on an undulating twill pattern on my little 4 harness glimakra table loom. The warp is 20/2 pearl cotton in yellow and the weft is one 20/2 mercerized cotton in a dark almost black purple and one thread of 60/2 silk in a brighter, lighter purple. The tension is off one one side, or so it seems, so that the left selvedge shifts around as it goes over the front beam. It doesnt appear to have done that in the sampler but I only had about 4 inches in this same weft. My teacher told me to maybe put a cloth behind it as it goes over the beam, but I havent tried it yet. She said that is why she stays away from things like undulating twills, because they have to go over so many threads at once and they destabilize the cloth, especially by having many consecutive threads on the same shaft. It makes sense, and both yarns are slippery, but I want to make this work. It makes me get very nervous that it isn't perfect, and I almost want to stop, but the only way to get better is to just keep weaving. At least it will help me get my beat better. I'm honestly embarassed, this thread combination shows EVERY inconsistency. The upside is that it is very irridescent and the design features a psychedelic eye and star at different intervals, and those things together might coverup the imperfections in the final product.
The other upside is that this is the first piece I have made on my own where I tried a new threading, altered mathematically to suit my needs, wound a flawless warp of a finer than usual thread, made a bunch of new heddles and put them on this table loom, made a lengthy sampler of several different wefts and washed and dryed it before starting on the final product. Though it may not be the finest cloth in all the land, I learned a lot making it and...
listen to me,
this cloth is only 16 inches long so far. Why not finish it before I start referring to the experience of making it in the past tense!? I am a dramatic soul. It doesnt help to stare at undulating twills either. Im just figuring out how you can alter the way the round eye part of the pattern looks by changing which shaft you make your reverse at. Weaving makes me feel so good because I can follow a pattern really deep and then I start to see it opening up inside of me and I can see where it comes from and what its permutations are. Wheeeeeee.......Im looking forward to designing a draft of straight and undulating twills with a different warp color for each in the same cloth and treadling a straight twill with a weft color as the same as the straight twill warp. I think that will really make the undulating twill pop. Then you would get just some vertical stripes of the iridescent.
But first, Im going to do a plain weave. Nice, simple, good ol wool plain weave.

after the fact and pictures:
i only made samples with this and now re-looking at them i see where if i was being more consistent with my beat, and just an overall better weaver, I could still use this pattern and get something good. I made two small wall pieces, not even a foot each for my mom and a friend using a wool as a weft, which made the slipping much, much better.
Here are two pictures of the sample with purple mercerized cotton/purple silk weft.

You can see in the image on the right how the selvedges were slipping. It is a really cool design though!