I just finished mine and I took 3/32" balsa and made it just a little larger than the space. I wet them on one side with Windex to get them to bend a little and then put them in place. It is not an easy job, and I had to do a couple over in order to get them to fit right. However, I think if you leave them out you may run into problems. These spacers are used to attach the covering to when you start to put the film on the rear of the fuse. Here is a pic of my completed SE. (Finished Last Week)

http://www.rcuniverse.com/forum/Fina...1914644/tm.htm

Sorry the pics are pretty smal when you click on them. Go to the thread above and look at the pics. You will see that you should have something behind the canopy and ahead of the tailfeathers to attach the covering to. I would recommend putting the webbing in.