I don't have exact mileage, but if I had to guess I'd say that full loop is 9ish miles. If you skip the castle climb it's maybe 7.5-8ish. What's nice for an after work ride is that it's not all singletrack, it's about a 65/35 mix of singletrack and fireroad so you can spin a bit. I might hit Ramapo after work tomorrow, if that happens I'll GPS that loop
Do you pass a private residence before the castle ruins?