Squirrels will often muscle up the flashing. You may need to paint it with a blend of motor oil and grease. Straight motor oil requires frequent apps and grease by itself can be thick enough to give them some traction. I use about a 3-1 ratio oil to grease. Of course squirrels are capable of a vertical leap from the ground of almost 4' so trees need to be trained with long trunks or at least with steep enough scaffolds to shape a cone that high.
If I have enough trunk before scaffolds to construct these baffles and there are no launching pads close by (squirrels can jump much longer horizontally) I get 100% protection from squirrels using this method against grey and red squirrels at dozens of sites that lose at least all pears and peaches to squirrels otherwise. The only failure I ever have is if the squirrels keep trying to get up the metal until they've removed the oil-grease mixture- and this is a small percentage of locations, but I've started repainting the metal every couple of weeks where this happens and reapply at least once at most other sites.
I should also mention that like most rodents, squirrels can squeeze through a narrower space than you'd imagine so the metal has to be stapled pretty tight. The metal also should be removed after your gratifying harvest- promptly. Peaches have sensitive bark.
Coons and possums are stopped by metal alone.
Birds don't seem deterred and probably appreciate the tranquility of a restaurant without distractions. It gets complicated when nets and baffles are required but is doable. Just don't let the nets sag below the baffles. 5' before first scaffolds would be helpful for this.