I've never had a trumpet lesson from anyone; yet, played 1st chair and lead all through college although not a music major. I've played some pro gigs since my college days. I can double tongue, triple tongue, play legit with a good tone and loud from a double pedal tone C to a double C. I play slightly to the right with a pivot. What matters is the sound and tone you produce. These people who state that you MUST definitely play this way or that way with this mouthpiece or that mouthpieces etc. ad nauseum simply don't know what they are talking about. We are ALL individuals with differing facial features; oral cavities; tooth formations; lip sizes and I could go on and on. There are great players who play dead center of their lips and great players who play off to the side. There are great players who play (relatively) small equipment and great players who play (relatively) large equipment etc. Do what works for YOU. A good tone must come FIRST. Endurance, range and technique are a matter of spending a lot of time practicing the right things. Probably the biggest single thing that took me a while to figure out was how to properly increase my air velocity for the high range.