Thanks for the ideas. I am going to see if I can weight the spindle a bit, and I also have some other roving I'm going to try. (bought a kit to knit a scarf from roving at a wool festival last year, and I'm going to have some lovely roving left over from that - can't wait to finish the scarf so I can try to spin the leftover!). I think the second roving won't be quite so thick/heavy, so maybe that will make a difference.
Thanks for the advice, etc! I appreciate it.