A G5RV should have very little if any gain there as it is only slightly
longer than a dipole cut for 5 MHZ. That comes to just over 93 feet total
length.
I'm sure someone can tell you which power setting to use with the 706. I
think they change in 20 watt steps, but I'm not sure since I don't own one.
It will be interesting to see how many people jump onto this band, how long
the frequencies are so tightly restricted, and how long before they raise
the power limit to 100 output.
I also think that people are going to be pleasantly surprised at how well 50
watts will play on a non-crowded frequency.
Unfortunately, it will also be interesting to see who tries to dominate the
5 channels.
Mike Duke