I'll try to post pics ASAP... I used tape to hold the gauges down flat against the old gauges. Otherwise, if there is a high spot, one of the needles could bind up with it.

The high spot that I had (where my speedo gauge stuck) was in the center of the speedo gauge. Taping down the edges wouldn't remedy this until I pulled the edge tight and then taped it. One thing that would be handy though is double-sided scotch tape. I think that stuff would be perfect for holding down the inner area of the gauges. With regular scotch tape, you are limited to taping down only the edges.

...oh yeah, spray-on glue would work well if you wanted the gauges to be permanent. But it would be very hard dealing with slipping the gauges onto the needles without it getting stuck everywhere and making a mess. If the needles could be removed/replaced easily, it would be best to take them off. It would make the whole job a lot easier. I don't think this is recommended recommeded to remove the needles though.