All your horses are gorgeous. =) Solid base makes me think of your position in the first pic- yea, you could be releasing a bit more, but you have a very..tight and together position. :) and as you said, your horse looks great. But you look pretty good in all the pics, aside from a few tiny exceptions like letting your lower leg slip back slightly and your back get too low.
But overall your position is great, I would trade anyday! ;)
And I am soo jealous of your leg position in those last two photos..