But I'd really suggest getting a saddler out. There is a lot more to it than just clearance. A saddle has to balance front to back, so sometimes what the text book says and what it is in real life can be 2 different things.
This is what I'm lead to believe, the old finger rule is long gone, it is " sufficient clearance" but in your case as your so unsure the saddle fitter route is the way to go
It totally depends on the saddle, the horse and the rider! Some saddles I fit might only have 1.5 to 2 fingers once the rider is on and the saddle has bedded in, some might have as much as 4.5 though that is rare.
It's much better to know how your saddle should fit - then you can monitor the clearance for your personal set up. If you press down on the pommel and run your hand down under the panel from the gullet to the points, the pressure should feel even, and when you look from the front, the point pockets' (on the sweat flap, where the tree points sit in a little pocket) stitching should line up at the same angle as the ribcage on which the saddle sits.
I try and encourage my clients to know when the saddle is too narrow or too wide through these checks - if a saddle doesn't fit it will be tight somewhere, whether too narrow or too wide, so it's not a very helpful term .
Hope that helps, and definitely get a good fitter out to check it.