Not a complicated thing to do, just use the SIP's screws for the attachment. 24" on center is more than enough for solar panels, I have done it on 4' centers. If the brackets used for the raking system doesn't accomdate the sizing of the sips screws simple find a lag bolt long enough to penetrate into the support beams.
As for leaking problems, there are some great systems for counter flashing the brackets for the racking system. Just don't let any installer tell you that simply adding some silicon will do the trick, this will fail and so will your roof. here is an example of one flashing system, but most if not all mounting systems have some method of flashing.
http://ngeus.com/NGEwebsite/content/pdf%20files/racking/zilla4web2.pdf
good luck
Tom Pittsley
[email protected] www.eebt.org