I want to pump...

…but I dont want to lose my upward curve. Is this possible?

If your curve is mild and your tube is sized correctly, you’ll keep your curve. If your curve is severe, pumping will tend to correct it.

It’s hard to say what’s “mild” and what’s “severe” to me, because I have nothing to compare my unit to. I think I’ll post pics in the pic forum, and let you guys tell me. :D

Also, how does tube sizing affect curvature correction?

If the tube is only a little thicker than your shaft, then as you can imagine the hard cylinder will only allow your unit to curve a certain amount. Over time, the enlargement you get from the pump will be enlarging you, while also encouraging your unit to conform to the cylinder shape.

Or you can try doing your jelqs upward to promote the upward curve.