@3run the model exceeds 4000 units in length so I believe a sprite would not be allowed. However it is to large either ways so I will replace it with both 1024 long models and sprites to see what gives the best results.
What you mean by units? Quants? Having one sided model with 4 vertexes and with size bigger than 4000 quants won't kill framerate too I think. What is the size of the skin you use for that model? Simply create sprite and scale it up! Let's say sprite with size 1024x256 (wide image for landscape) placed in exact the same position and scaled up too 4000 quants, it won't kill the framerate!
BTW about 4000 quants, make sure you set clipping settings for camera, so objects far than let's say 5000 (it could be different value of course, depends on how far you would like to see things) quants aren't going to be visible. I remember I had same problem at the very beginning when I used to spent more time on creating levels and placing models (without LODs) all over the place, then suddenly fps used to drop bellow 40-30 frames, only cause they used to get visible all at the same time without LODs, with shadows etc.
Greets!
