I do a lot of off-leash hiking with Roo (my RR) & Abby (my mix). I started them off-leash right from when they were pups. Of course, since my two are both sight hounds, they will chase when they see something. Sometimes, if I call they will break chase, others times no. However, when not on chase (or going to greet another dog) they have about 99.9% excellent recall. Actually, I never used treats to encourage re-call, just verbal praise and sometimes petting.
A few suggestions for training:
1. Use a long lead and hold it loose (in open areas) for training.
2. Go to safe enclosed areas (perhaps a school yard) for off leash training once Ghillie "graduates" from being on leash.
3. A good training technique is to move away from your dog instead of towards your dog. This will often trip the "chase" instinct so your dog will come to you.
One more thought is that I almost never (insofar as is humanly possible) yell at my dogs. I do not yell, partially from my own temperment and also partially by design because of my off-leash lifestyle. If you "punish" by yelling at Ghillie, how would your dog distinguish between a "punishment" yelling and a loud "come" command ?
In the end, the dog has to trust and want to be with you enough to offset it's interest in "freedom". As far as the chasing squirrels go, you may never be able to do more than to partially offset the chase instinct.
Hope some of this helps,
Litter announcements / solicitations are by approval of the Administrator/CoAdministrator- only.