I have the Collegiate Levanto and I really like it, but I think to decide you need to sit in both and try them on your horse and see which one is more comfortable for you and the horse. It doesn't matter how nice a saddle is if it doesn't fit right!
Gallant Gesture "Liam" 1995 chestnut ottb gelding
Mr. Painter "Remy" 2006 chestnut ottb gelding
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What do you ride in - I think you have a Bates - generally go up an inch when you move to a dressage re the deep seat & wanting room to sit "back" ... tho if your filly has a very short back you may need to compromise on a saddle that fits her vs the saddle that fits you.
Try both if possible.
ETA the Kieffer is more adjustable & with a young horse I weight this more heavily
A deep-seated saddle feels smaller to the rider than a similarly-sized open-seated saddle. So if you're comfortable in a 17" saddle (and having a full hand's width between your seat and the top of the cantle is normal), then a 16.5" would probably feel too small even in the same style of saddle. If you're also switching to a deeper seat, you're likely to feel as though you've been wedged in.
Also, the smaller the saddle, the more concentrated the weight is on a smaller area of the horse's back. This can cause some soreness issues for the horse.
"The formula 'Two and two make five' is not without its attractions." --Dostoevsky
Yes, I have a Bates, which is a 17" but I can fit my whole hand behind my seat, so I thought 16.5" would be o.k...?
Alto, I have heard they are more adjustable, how is this? Restuffing?
The tree is adjustable through a certified fitter - contact Kieffer USA for more details (also a good source of information on that particular saddle especially if you give them the serial number), AFAIK the Kieffers are almost all wool flocked.
The newer collegiates offer a foam lined panel with wool (synthetic) mid layer - the 2 saddle fitters local to me will not adjust these saddles (they might completely redo the panels if the panel leather is appropriate but that is a major cost compared to adding/removing wool) so talk to your local fitter about this panel.
I find it that many retailers of these saddles do not state that the wool used is synthetic or that adjustment is not the same as a straight wool panel.
This panel construction is not unique to the collegiates, Pessoa also uses a similar panel but very clearly indicates the construction rather than advertising it as "wool flocked".
As these saddles are on (good) clearance, ask about warranties - the shop may not want to deal with any issues & you may need to ship etc directly to the manufacturer (which is difficult if Weatherbeeta is the distributor as their policy is to deal with tack shops etc & not individuals).
My kid rides in a 16 1/2 - 17 CC saddle & squeeezes into the 16 1/2 County dressage which fit FP perfectly it's been great for his first year u/s as she never actually sat down on his back - this year we're shopping for a CC that will fit both horse & rider