I have tried floating the top and batting using the narrow clamps. Maybe it's me, but I did not like it nearly as well as not floating the top; I get better results by not floating. I do think the wider clamps (sold on Jamie Wallen's site) would probably be better. Have not done any price comparisons.
Here is a link to the wider clamps:
http://www.quiltersapothecary.com/to...arm-tools.html
I got the Harbor Freight long magnets, but again they didn't work all that well for me. They are very strong and were difficult for me both to position correctly and then to remove (in order to re-position). Paradoxically, I also had a problem with them falling off unexpectedly (after I rolled the quilt without re-positioning the magnets). It may be a skills problem on my end, but so far attaching the quilt top bottom to a roller has worked best for me.