I agree with Les, for as short a time as you had with Mark you've created a good shape especially as it's natural edged and as you note, your first proper turning.
Les also suggests a good way to reverse the form, I have another way, but it does depend upon having wall 2" or 3" insulation (Kingspan) or similar to hand. Glue it to a bit of scrap wood and then the same as Les, bring up the tail stock and tighten. The difference is the insulation conforms to the inner curve of the form perfectly.