"Is the gain and angle here about what you might expect the difference to be?"
the sigma's advantage in gain over the 5/8wave in your model is slightly higher than avanti claimed for the stock sigma eddie, i imagine 1 db or so is in the ballpark,
the difference in how they perform here is more than the gain advantage indicates,
it would be interesting to see how the sirio compares to the cte top-one mounted at the same tip height, the astroplane is a strange antenna, the sirio is also a little different from the norm, does the sirio achieve the same results,
do you think the astroplane does what is claimed eddie, providing more signal at low angles than a 5/8wave when used under the fcc height restrictions/ tip height limit above house/property for which the astroplane was designed?
i can't help with the wolf antennas, having the gamma tube open to collect rain is asking for trouble at best, its where i would look first if i had high vswr on that antenna 
