Hi Karl,
You might be better off fitting the SA in front of the lens instead of trying to shoe-horn it in between the lens and camera. See my meteor spectrum here for example.
http://www.threehillsobservatory.co....spectra_20.htm
You could then use your 8mm FL lens to give you a wide field and the best chance to catch one, though the spectrum will be rather low resolution (roughly double the length of one on my website) Alternatively the 35mm lens will give better resolution but a narrower field.
Cheers
Robin