Echinopsis Hybrid repotting question

[Arizona Jeanie]

Hello all, maybe someone can help me out with this. My first and only Echinopsis is ready for re-potting. It was given to me as a pup about three years ago, the giver didn't know what it was, kept it as a house plant, and never had a flower. Well, the pup rooted and grew, and was sufficiently mistreated to flower this year--bears a resemblance to "Anastasia", but who knows. It's trying to be columnar, and has no pups. Here's my problem: the whole thing is shaped like a hot-air balloon. (Sorry but I don't have a camera.) The base is about 1.5 inches diameter, the widest part is about 4 inches diameter, and overall height is a little over 4 inches. When I repot, should I drop that narrow base down into the potting mix a bit, or leave the soil line where it is? Is this even the right time of year to move it? Any other potting tips? I don't know much about these plants, but the flower was spectacular. Thanks for your help!