Try just sticking the antenna in an overhead cabinet. Some folks have reported good success with that. I routed the wire for my Onyx antenna through an existing rooftop weather tight wire entry port that I installed for other antennas. The magnetic antenna sits on a steel panel that was added to the roof for mounting other magnetic antennas for cell service, WiFi, etc.
Dutch
2001 GBM Landau 34' Class A
F53 chassis, Triton V10, TST TPMS
Bigfoot Automatic Leveling System
2011 Toyota RAV4 4WD/Remco pump
ReadyBrute Elite tow bar/Blue Ox baseplate