You are correct, I built this model: www.user.dccnet.com/jonleblanc/Canada_TV_Stations/Gray-Hoverman/DBGH_VHF_hi_Antenna.pdfIs this the design for your DBGH with L1 and L2 for CH13?
Forum member holl_ands does antenna modeling. He might be able to answer your question about how well your current DBGH will do on CH7.
Optimized for channel 13 (L1 = 28", L2 = 10"). This would probably be called a DBGH6n2 (only 2 NARODs per bay).
NARODS on this antenna are just horizontal straight, not hat-shaped like the models at nikiml's Antenna pages. I guess therefore I cannot go by the gain sweeps shown for those models.