I've installed quite a few XM/Sirius radios in coaches. I have never had good luck with the antenna anywhere inside the coach. I've never tried a side mount. Based on my experience, I will only help do this if they are agreeable to the roof mounted antenna. 100% of the roof mounted antennas work from day one, without any trouble.
2005 Newmar KSDP 3910 + GMC ENVOY XUV 37K lbs Moving Down The Road
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Nobody Knows Your Coach Like Somebody Who Owns One Just Like Yours