Present theory calls for the exclusion of longer vacuum fluctuations (aka larger virtual particles) in favor of shorter vacuum fluctuations (aka smaller virtual particles) that can fit an integer number of times between the Casimir geometry (plates) but a relativistic interpertation based on a paper by Jan Naudts would better fit the results claimed by Black Light Power and other researchers investigting
atomic hydrogen reactions with catalysts.
see animations and blog
http://www.scienceblog.com/cms/blog/7200-relativistic-interpretation-casimir-effect.html-1