I’ve used the SG Labs transverter with the supplied antenna attached directly to it, and had some good contacts on SSB and FM (driven by a Wouxun handy on one occasion).
Suprisingly good results, and on a nice day the transverter with antenna attached sits well on a trig point. Just lay it down flat to change polarisation. Yes, I think vertical is the norm for FM, I have worked a couple of fixed stations with “white stick” antennas.
Because it is so light, I have tried holding it at different heights during a QSO and found no great difference from waist level to arm at full stretch up. I’ve not tried it at 30cm, I think that might be a bit below optimum unless you are close to a steep drop off - interested to hear how you get on.
Edit: Activation log from Pynlimon GW/MW-001