I have no idea about the size of the OEM tank, but if it is too expensive and a smaller, less expensive, tank will fit I'd say go for it. I fill up my propane every couple of years whether I need it or not. The stock tank is a monster and unless you camp regularly with Admiral Byrd in the Antarctic I think you can survive with less propane capacity.
Just my opinion, of course.
Pat in Menifee, CA
www.patcarnathan.com
2009 Mandalay 43A
2009 Honda CR-V Toad
2011 Toyota Tacoma
2013 Honda Goldwing
2003 Honda TRX400ex (2)
2005 Honda Aquatrax F12-X (2)
2016 Yamaha YXZ1000R