I'm about to weave a large tartan project. I have an 8 shaft loom. I know I only need 4 shafts to weave it in 2:2 twill, but I'm wondering if I should thread it over all 8 shafts. Will it balance my David loom better?

There really isn't a need for that unless you will have too many heddles at the sides of 5-8. This will be a problem if you are weaving the full width of the loom.

Thanks!