If I am reading between the lines correctly, you have a line of sight issue for the 119 satellite, yes? If Directv uses the 5 lnb for sd local channels in your area, they will not install a 3 lnb. An independent installer might, or you could do it yourself. Like Jimbo asked, what DMA are you in?
All of the HD locals are on 99 & 103 which would be a slimline 3
The only way a slimline 5 would be installed would be under one of these 4 options
-not all the locals are in HD and the SD ones are on 119
-customer gets a SD only receiver with the HD ones (god knows why)
-spanish programming
-thats the only thing the installer has on the truck