Yes, you can use almost any citrus variety as a rootstock for any other variety. There are a very few combinations that don't work. But calamondin doesn't have any particular advantages. It is not cold hardy, and I don't think it will have a dwarfing effect. Only Poncirus trifoliata Flying Dragon is used as a dwarfing rootstock, but as in your zone you are probably growing potted citrus, it is the pot size that controls plant size much more than the rootstock variety.

From everything I have read, and from my own experience, calamondins are quite cold hardy. In fact, they seem to be one of the most cold hardy citrus. I have had cold damage on a number of my trees over the years, but never on a calamondin so far. I am in zone 9, so maybe my definition of cold hardiness is not the same as for someone in the UK or WV.

Yes, Calamondins have good cold-tolerance, but nowhere near the cold-tolerance that traditional citrus rootstalks have, like Trifoliate Orange (hardy to around zone 5, well below 0 degrees) and Sour Orange (hardy to zone 7 or so).

Flying Dragon and Poncirus trifoliata orange impart the most cold tolerance to citrus however in severe freezes they need more protection. In the sever freeze of 1983 we lost 70 large trees. In the severe freeze of 1989 there were 9 satsuma trees growing in the back yard at Nederland TX. The were banked to 3 to 4 feet in height. The tops were lost but saved above the bud union. The Brown Select, Louisiana early and Early St. Anne were seedling trees that were growing at Port Sulphur LA and were lost. However Joseph Ranatza, owner of Starfarm nursery had obtained budwood. He banked his trees that were budded the fall before the freeze. His buds were saved by being banked. If it had not been for him these cultvars would have been lost.

I have heard that in 1989 one of the research stations in west central Texas froze hard and that the only trees that survived were grafted to sour orange and that all the trifoilata grafted trees died. Has anyone else heard that story? I have always heard that trifoliata is more hardy but I heard this story from a very, very credible source. I am curiuos as to anyones opinion on this and I hope people see this.

Thanks,
Scaper