Dave,
I'm in a similar boat on this RV conveyor belt of life but a few rollers ahead of you. I thought I knew what I wanted but after reading one Solar thread on here, with a plethora of wizards, I was then sure I knew nothing. We are finishing up the install of the two Renogy panels that Buzz wrote about. I'll post up the results soon. The Solar panel product industry is changing so quickly, it is VERY important to have a mentor who is up-to-date on what's out there. It's really pretty simple. Problem was, I had no idea how many watts I needed for my particular set up. My guru was Jim (BigfootFord) who guided me through the Solar Swamp of choices. So many choices because everyone's conditions and requirements are different. Also, companies come and go like the wind. (Solindra?)
However, the idea is to get as many Solar panels as you think you will need (and will physically fit without too many shadows) and then some.
With a Lance 1181, you should have a lot more space on the roof than I do allowing you to install wider panels. Jim's idea was to make cardboard templates of the panel footprint and place it around to find the absolute best placement and to see what size would be best.
jefe