I've had the same problem with yellowing from the Testors clear gloss laquer over white. It really ticked me off to get all the way to the final finish and have it go yellow in the thick areas.
Yes, you can use clear laquer over acrylics, but I've found that Future gives as nice a gloss, if not as hard a finish, and is MUCH easier to use, clean up, and cheaper to boot.
True, you can polish the laquer to get a great shine, but the Future won't need it anyway. Less work and less chance of problems for a great finish.