1.5" is a good depth for your tap hole.
Reds and silvers can be very finiky on buckets. They have a tendency to not be the best producers. They perform much better on vacuum. Even a little bit of vacuum can make a big difference. My first year I did buckets with 25 taps . I think the most I got in 1 day was 10 gallons. My trees are mostly red. The same group of trees on 3/16 tubing with natural vacuum will give me 10 gallons on a slow day and 40 on a good day like today.