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Yeah, more information will be needed. As you can see in the store, there are several sizes of trays depending on what kind of pack you are using.
When choosing your tray, it is best to measure the lipos personally because the published sizes for lipos usually is not what they are in reality. Also, when choosing a tray, you might want a little more room in the front and back (especially the front) to add some foam padding to protect the packs during lawn-dart landings.