Citrange is the most common one used in Australia for Fingerlime cultivars, and seems to have good results.
A lot of the grafted trees are going to be grown fairly close to the natural range of the plant, so any dormancy due to Trifoliata may not be wanted.
I have used citrange, swingle and rough lemon,but not had much luck with
Trifoliata,but I think others have used it.
Some people in USA and Europe may be dealing with fingerlime hybrids, which may be more Trifoliata compatable ?
The true Fingerlimes, Microcitrus australis are wild plants, so each selection is variable in many factors, including best rootstock to some degree.
If you have enough buds, I would try both, Swingle should give you a bigger plant faster.
Anybody using Trifoliata for true Fingerlimes ?