Two thoughts: (although I can't yet claim to be an expert on witness points, I have researched them extensively since my epiphany and even talked to a luthier a bit more about them).
Being vintage, and a 4 string, the effect of witness points on your Guild will be a bit less extreme than that what I experienced on the heavy .130 gauge B-string.
That force exists already on the rosewood saddles of your bass simply by being strung up to tension, although caution is certainly warranted. I think the main idea is to remove any latent arc of the string, so the minimum force to do this will accomplish the setting of witness points.
I believe, but do not know, that technically speaking, the straightening of latent arcs that setting witness points provides would eventually take place just by having a string up to tension. Setting points just hurries the process. They do it on mandolins, some of which also have wood saddles.
That Guild of your seems like a cool instrument. A vintage shorter scale in that vein or maybe a Starfire is on my "wish-list"