I was told by a good source that it's better to wait overnight when
clearing single stage colors.
Single stage colors off gass a long time.
When I cleared my car, that I used a metallic urethane on,
I found if I didn't wait a good 3 hrs, sometimes the metallic would
be disturbed by the clear and make the color look different,
looking like stripes.
Waiting longer, up to 24 hrs is best.