For comparison, on my 40' unit currently in Albuquerque NM, the ac runs virtually all day in 95-100 degree weather with the thermostat set at 79, and keeps us in the 80-81 degree range or cooler. I always put the big awning and door awning out first thing in the morning to shade the SE side of the coach from the sun most of the day. That definitely will help some.
I have never heard of one of these basement air units needing addition of freon. In fact, RVP and their service manual says no maintenance is required other than changing the filter, emphasizing that they are sealed units and require no freon servicing. You say the shop where it is added the valve? I cannot imagine they are an RVP trained/certified service center. I have had problems letting places work on my unit when they said they were familiar with them, but obviously were not RVP trained. You can find certified service places by going to the RVP website at [www.rvcomfort.com/rvp/rvp.php]
. Personally, I think you are chasing up the wrong tree & wasting time and $$ by altering the unit so you can check/add freon. In addition, adding tubing etc outside the unit will only make it more of a problem and cost more labor to remove when it needs cleaning, blower motor replacement, compressor replacement, etc.
There are two reasons I have seen for these units not cooling well. The easiest to diagnose is that only one compressor is running. From your comments on amp draw, that apparently is not your problem. I see apx 17 amp from the first compressor, and a total of apx 24 with both running. The other reason ...and #1 reason for cooling problems ...is a leak and/or separation in the duct work going from the basement unit to the roof behind the rear cap. That is normally easy to diagnose, but may be much harder to fix depending on where the leak is. Some have found the leak by lying on the ground at the passenger rear corner with the ac running, and feeling the cool air escaping. Others have found it by getting on the ladder and feeling the rear cap from top to bottom on that side with the ac running on a hot day ...the cap will feel cooler where the cold air is escaping inside the cap. Duct separation/leaking seemed to be a big problem in 2004 models. Some have resolved the leak(s) with aluminum duct tape. A few have had to have the rear cap removed to get to the leak area.