1. In terms of feel, is a treeless saddle about halfway between a bareback pad and a traditional saddle? Or closer to a bareback pad?
A quality treeless saddle feels very little like a bareback pad. Especially ones like the Ghost treeless, which have an actual twist to the seat so you sit narrower.
You can post and two point as I am doing here.
Without the solid tree there is a slightly bouncier feel to posting, but you can rise out of the saddle easily.
This is in contrast to the "treeless" which are cheap, glorified bareback pads.
Here I am riding in a "treeless" which although it has stirrups they could never be used for mounting and it will slide to one side (notice the breast collar for safety). The underside is flat. Hopefully you can notice the lack of structure. These are the ones people say it is unsafe to use stirrups with, because you could get the weight in one stirrup and pull the pad over.
5. Itís not like Pony has any withers to hold a traditional saddle in place, but still, I have to wonder: without a tree, doesnít a treeless saddle slip around more?
6. I keep reading that I need special pads with a treeless? Is this the case with all treeless saddles? Why do I need a special pad? Why wouldnít the saddle just have whatever padding it needed already? Or is this just some treeless saddles?
To see if you need a treeless pad, what you do is check to see if you can pull a lead rope through the channel of the saddle when you are on the horse. If you can do so easily, there is spinal clearance and you don't need a pad. It is doubtful you would need one on a real treeless with a channel. Especially not on a round horse. A person would need one if they were heavy enough to squash the center of the channel down onto the spine, or if the horse's spine protruded high off the back into the channel.
Treeless saddles are not one size fits all. That's the main reason why they have the changeable seats, because you can extend the seat to make the base fit a larger person.
I have not had any issues with pressure points, because I make sure the saddle clears the spine. The structure of a quality treeless will not cause issues even if you post or two point extensively like I do.
Some things I have noted:
They are as secure as a saddle if a horse bucks or spooks, and I have stayed on through some crazy moves.
One way they feel more like a bareback pad is that they don't "clamp down" on a horse's body so for example if a strong horse is galloping and pulling, you do not have as much support - the treeless will want to give toward the horse slightly, which means your core strength feels a little less powerful for the horse. I did not notice this effect except for on a strong horse when going very fast. My solution was to use a little more leverage with her bit.
When I used too much padding (a thick treeless pad, thinking it would be kinder), on my round horse it did cause the saddle to be less stable and want to slip a little to the side. It also made my legs sit wide, which made me less balanced. I weight 125 lbs so I just used regular english pads under my Ghost saddles.
They are not like a bareback pad. On a bareback pad I sit wide and my legs get tired from squeezing and trying to stabilize at faster gaits. Treeless have enough structure to allow you to ride much longer without using too much muscle strength.