If a saddle is pitching the rider forward, does that mean it needs to be built up in front or behind?
The front would make sense to me, so the saddle is more level, but someone (who seemingly should know), suggested it should be built up in the back more so the rider leans back, making them actually sit straight?
The saddle looks level, (the seat and depth of seat), when you put it on.
I also argued that it could just be that the rider is leaning forward, but someone else got on and said that yes, it made them feel like they should lean forward slightly, too.
Horse is back in training after a long lay off, so short of having the saddle re-flocked right away, what would you do? Saddle doesn't seem to bother the horse in any way...no dry spots, goes just the same in it as in other saddles.
Your beliefs don't make you a better person, your behaviour does.
I would also agree with adding a shim to the front(withers), however this will change the whole balance of the saddle and it may just not fit the rider. I just went through that with a student!
You mentioned that the horse has been laid off for a long time, so it is safe to assume that he lost all top line muscles. As he gets back to work, as long as he is worked over his back properly, some of this should build back up naturally and you might be able to remove shims again at that point.
It could be that the saddle needs to be lifted in front - it's common for the rider to be pitched forward if the saddle's sitting pommel-low. However, there are other issues that can cause a rider to pitch forward, such as too high a cantle/too small a seat, too narrow a twist or the stirrup bars being set too far back. As joiedevie99 pointed out, arbitrarily shimming the front may throw off fit for the horse. Do you have a local fitter who could come out and take a look?