What theoretically is the smallest cyclic trans hydrocarbon to correspond to a local potential energy minimum?

[Trans-cyclooctene](https://en.wikipedia.org/wiki/Cyclooctene) is isolatable at room temperature. 


[Trans-cycloheptene](http://pubs.acs.org/doi/abs/10.1021/ja055388i) is also known at low temperature. 


[Ab Initio Conformational Analysis of trans-Cyclohexene](http://pubs.acs.org/doi/abs/10.1021/jo00109a047) (1995) says that there is spectroscopic evidence of the existence of trans-Cyclohexene, but that trans-cyclopentene hasn't been studied. 


So I'm looking for any further information on trans-cyclopentene, trans-cyclobutene or trans-cyclopropene, particularly whether any of these have been theoretically calculated as (or ruled out as) corresponding to a local potential energy minimum. 


