The tunnel is plenty large for learning to freefly in, don't worry. Even though the Perris tunnel is larger, the Hollywood tunnel will be cheaper, more powerful and may be closer to where you live [I know it is for me!]. I've worked on my sit in the Hollywood tunnel and I'm currently learning head-down in there.
I wish it was bigger, sure, but it's still big enough to get done what you need to get done. As the windspeeds go up and you learn to grab the air a little better, you'll find that you spend a decent amount of time up in the larger area of the tunnel anyways.
Only once while learning head-down did I start myself in the "wrong" position, putting my feet in contact with the wall. I've also found that the tunnel isn't quite large enough for a back carve [at least when you're sloppy like me...].
So go for it! And dream that maybe someday it'll grow up to be a 12-footer... I really don't know what I'm talking about.