I wanted to give a good report for once especially for anyone else using a shield.
We had our one month well-baby check up today and got to get an official weight gain. At birth he was 5 lb 13 oz. Today he is up to 8 lb 12 oz - just 1 month and 4 days later!
It really makes the always frequent feedings and lack of sleep feel worth it.
Also, there was obviously no issue with the shield causing transfer issues.