As mentioned in the About section, I have almost always used a single sheet of glass for my backgrounds since it generally allows for fewer lead lines and provides greater continuity within the panel while reducing abrupt changes in color and texture. I should note that there are several problems inherent in the use of a single sheet of glass:                                                                                                                      1. Depending on the size of the panel it may be necessary to cut large and sometimes full sheets of glass which can be somewhat more difficult than working with smaller pieces of glass.                                                                                                                                       2. Since you are utilizing a single sheet of glass an errant crack at any point during the construction of a panel will probably ruin the work, which can be very frustrating. Occasionally a crack can be incorporated as a lead line but the glass is rarely that accommodating.                                                                                                                      It is certainly not necessary to employ only one sheet of glass in the background of a window or a panel, it is simply one of my idiosyncrasies. The array of sheet glass available on the market is almost overwhelming ( I do make some personal observation on the subject in the color post )  but the choice is up to you.