I think I did that above ?
1st, there is only about 4 HD channels on 110, the 1st 4 that dish added in their HD lineup. 2nd, the 622 is a dual tuner and legacy wouldn't work on your setup unless you had a dual lnb, if you could upgrade the lnb to dish pro dual on it, it would be fine.
I take 2 211's with us camping and have two HDTV's for the RV, when I am going to be at a spot for a while like a week, I will take my portable dish 500 and hit 119 and 129 instead of the normal 119 and 110, that way I get all the HD and 119 has most of the non HD we watch too.
The 622 has a hard drive and I am not sure what all the movement would do to it ?
If you go with a 211, you can keep your same setup, hit 110 and get a few HD channels and of course hook it in with your RV antenna and scan in any digital locals, that will give you some more HD possibilities. If your in the mood for just HD, you could crank the dish around and hit 129 or 61.5 and get the rest.
Or you could upgrade the LNB in your onboard dish to dish pro, then add a DP44 switch and bring a dish on a tripod with a dish pro lnb and do a combo thing, hit 129 or 61.5 with your onboard, hit 119 and 110 with a portable dish 500 or leave the skew alone and just hit 119 with it. Hook the portable dish input to a DP44 and the input from the onboard, then use a dish seperator on a cable from your dp44 and hook up that 622. You could also have OTA digitals from that too and record away. You could whip out the tripod on those longer stays.
To get the 622 to work, you have to have a dual legacy lnb on your onboard, or you could point current single lnb onboard to 119 like usual and run a cable off a legacy dish tripod and hit 119, running both of these to the 622. You have to match each tuner with the legacy input or the 622 will not like it. Again, 119 from the onboard to the 622 and 119 from the tripod legacy to the 622, each tuner on the 622 must have the same Satellites available to it when using legacy or it gets really unhappy. Or upgrade the onboard to dish pro single and run to a DP44 and do the same on the tripod.
I would upgrade the lnb on the onboard to Dishpro single, then upgrade the tripod to a dish pro 500 dual and run these to a DP44 and then feed the 622 from the DP44 with a single cable and seperator. That way you could hit 129 or 61.5 with the onboard and 119 110 with the tripod 500.
Any reason why you want the 622 with no HDTV in the motorhome ? The 508 or any single tuner DVR would be a much easier solution and not require any modifications.