When I started I did mimic my tennis topspin groundstrokes, including switching grips. Over the last 8 months I have gone away from that. On my forehand side I mix between topspin or slice, but with the same continental grip. On the backhand side I do almost exclusively slice. The only time I hit a topspin backhand is if I get a short ball that bounces high - but that is happening with low enough frequency that my backhand slice is now better on those shots. Slice is great because it keeps the ball low on the other side. If they want to speed up a low ball they will need to hit more up to get it over the net, and those go long more often. Slice also allows you to put some side junk on it. People hate the side junk.