I don't know if this will help or not but I bought a heavy duty brother. It's a POS. The sunbrella will be 3 folds thick at any butt seam to tuck the loose threads in, if you join to ends you are now 6 deep, the room under the machine is really small so you will find yourself with a ton of pins and seam tape with layers of material gathered up trying to go thru that small space. The LS1 is great for sewing canvas and the LZ1 is for sails and other material you need a zig zag pattern, but take a look at how many times the needle goes thru the material on a Z run.
There are several commercial machines that have the raised arm, and are longer for the amount of material your going to put thru the space between the needle and the base.
I just got a Singer Ultra light from my grandmother, the machine is bullet proof but is a little small but I am planning on sewing a top cover for our 33. It's several panels of material, about 15'x10 I am hoping the singer does a better job due to the offset Motor, drive belt, and a handle on the drum.
If I was in the market I would buy a LS1.