Is it possible to change the default antenna on HS4? Because every time I start HS4, the antenna defaults to IDC Vertical, and I would like it to default to VU2 array.

No, that's not possible. The reason is, the IDC Vertical comes with the program for all operators and is working on all bands between 10 and 160 meters. It's the only one which can do it. All other antennas (paid or free) are only "additional" and must be selected for each (current) band where you are at the moment.

But there is a little chance: If you buy the "scanner plugin", you can save a specified antenna for each band there! Include the direction, output power (transmitter) and so on. If you start the scan and stop it on the desired band, you'll have always "your" antenna and settings.

73 and good DX from Jörg :-)
JO31ok
Bochum / Germany

Argh, I forgot something at my first post above! There is a second chance with the default program too:
If you save a frequency into the Memory (Freq. Counter, right hand) you'll have the same.
So just go e.g. on 40 meters, maybe 7.055.00 and set this frequency with a special antenna (and direction) into this memory.

So you can select 40 meters with all freq. later on with special antenna, power, MIC-GAIN and so on.
After clicking on e.g. a 20 meters freq. you'll get the next antenna, power and so on. So just save all important bands with at least ONE frequency there.

73 and good DX from Jörg :-)
JO31ok
Bochum / Germany