Found a used rotary dipole (actually three of them, for 10, 20 and 40 meter) that I’m going to use for fieldwork. Was able to establish QSO’s with J42OSEand SV2RSH in Greece on 20m today and the reported a 59. The ATU of the yaesu got it in resonance, there is no need for an autotuner with this antenna, the mast is roughly 6 meter in height and consists of 3 tubes, so this is nice for field trips. Will still look around for additional masts for a 40 meter wire antenna when I go in the field, but would like them from carbon.
The battery that I found has a 28Ah and runs on 12V, the only drawback is that the ft-991 reduces the TX power to something around 80W at best, and this slowly goes down to about 40W when the battery runs dead. This is good for 8 hours since the the ft-991 is mostly in receive mode.