The small three wheelers are called "Tuktuks" in other countries and the maximum speed of them is very low. The speed of my car is probably double, as would be the case of the Elio, if not three times.
The speed rating has to match the capability of the vehicle, in addition to the load rating; as I wrote earlier I would only use moped tyres on a moped.
I have no preference to use bias ply tyres, btw, we have to use what is available. There isn't much choice in the 16" wheel size and hardly anything in a radial. We (Liege owners) have been running our cars for almost fifteen years and this is an ongoing issue. We have researched the foreign market as well as our own.
I have to import the rear tyres I use for trials, from USA. Due to the low demand, the tyre dealer we use will only obtain four or five sets at a time and this results in a very high cost for what they are.
One further complication is that our cars are used for competitions as well as on the road and generally speaking, changing wheel and tyre sizes (or tyre types) isn't allowed. If you do this, you may be excluded from the event altogether or put into Class 8, which is the unlimited class, where we would no longer be competitive.