My personal method has been simply the plain 50 mg/mL in Wesson oil, but if I wanted to do a 100 mg/mL personally I would probably do the vehicle as one of these:
80/20 ethyl oleate / benzyl benzoate
78/20/2 ethyl oleate / benzyl benzoate / benzyl alcohol
Or the above substituting regular Wesson oil for ethyl oleate, or using a 50/50 mixture of the two. (I remember being interested in doing that a while back, but now I can't remember why!)
If using Wesson or other vegetable oil and if having used heat to assist dissolving I would make certain that the 100 mg/mL mixture wasn't over-concentrated (relative to the solubilizing power of the vehicle) by adding a speck of TP after cooling to room temperature.
If that doesn't precipitate TP, then a formulation is not overconcentrated.
If it does, it is.
While I haven't done it myself, my understanding from other people's results is that the above formulations with ethyl oleate would hold the 100 mg/mL.
There is nothing magic about the specification of Wesson oil above: it's simply what I use and it has always worked well for anyone who has tried it.