when you say that the La Spaz is finnicky and you have to work hard for a good shot, what results are you getting that would indicate that you arent getting a good shot at the moment?
I know that might sound like a silly question, but people judge their shots using different parameters. Some judge by the time taken for the shot to achieve the 30/60mls, the time to blonding of the shot, the taste, the absences of tiger striping or even the shape of the pour (if it doesnt look like a mouse/rat tail, it doesnt make the grade).
In relation to the use of that particular roaster to achieve your desired results, different beans and roast levels like different pour temperatures, and as the La Spaz has good temperature control, that will probably have a big bearing on your results.
Anyhow, let us know some of your symptoms and Im sure that there will be a solution forthcoming.
All the best,