After more than 5 yrs on this forum its still a mystery to me why some posts result in many replies and some get more or less ignored. Sometimes its the same old questions, or something that suggests no effort has been made to find an answer. In these cases I can understand why no-one replies, but there are instances where theres a debate or technical discussion to be had (at least in my humble opinion) that does not happen. On to your questions:
Oak gets mentioned every now and then on this forum. If you are a hobby maker oak is fine. The pros tend not to use it because the buyers want koa, mahogany etc and dont regard oak as a suitable wood irrespective of how the instrument sounds.
X bracing is used by some makers for baritone instruments or sometimes on archtop instruments. I have played a couple of inexpensive Chinese tenor ukes that were X braced and sounded OK but I think its fair to say few makers use X bracing on tenors,concerts or soprano ukes.
You may already know that most sopranos usually have no more that a bridge patch so X bracing does seem OTT ( I have no experience of white cedar). I also think few makers would use 3 back braces on a soprano: many tenors have only 2.
Vacuum clamping is often featured on the forum. I am not aware of shrink wrapping being used as a clamping system but maybe you are not the first to do this?
I am a hobby maker and encourage all to try new materials and methods and to share their experiences with fellow forum members
