Interesting, are you using a radial system when using the tripod?
Your screwdriver uses your framing and such on the RV for radials.
You may find this post interesting~
http://forums.qrz.com/showthread.php?t=93082
I know for a time when I had problems with my property and antenna restrictions I ran my HS-1500 on the roof with 8 each 10' radials which was what was recommended by High Sierra.
I was not impressed with it's overall performance but that's all I could get away with at the time.
That same antenna, mounted on my truck properly, with the same radio (IC-706) was outstanding.