Good advice, I practiced with one and a home plate on a tennis court next to my house (There was a wood wall that I used as a backstop) growing up and by the time I was 14 I was reaching 65-70mph (at least that's what the 80mph challenge kiosk said I was throwing at Dutchess Stadium in Wappingers Falls.
EDIT: I want to note that I was throwing every other day. And it really led to my development, especially considering the lack of seams forced me to throw the notion of throwing breaking balls out of the way. So, by the time the other phenomenal pitchers in my middle school league and senior league were injuring themselves and destroying their shoulders I was still developing.
I can't remember or not, but I think they're a little heavier though.