Here's the process I'm trying to attempt.  I'm not knowledgeable enough for real world procedures to know if this is a thing, but here goes.  I'm flying from KUIN --> KORD.

1. Here's my assignment page, which I feed into SimBrief.

2. Here's my SimBrief plan.  7000ft for a C208 seems reasonable.

3. Plan imported into P2A.  Procedures are to be determined by P2A.  Looking good.

4. Plan validated by P2A.  All's well.

5. File plan.  Everything goes pear-shaped.  My flight goes from 7000ft to FL230.  Service ceiling of the C208 is FL250, but that seems silly to climb all that way up just to come back down again.
So how do I fix this?

I can disable "Auto Load Recommended Procedures" but that just seems to address the problem cosmetically.  I expect ATC will still expect me to do that STAR even though the flight plan doesn't reflect it.  (I'm not sure about this though--I still get the STAR constraint warning is all)
I'm sure there are settings (either in SimBrief or P2ATC) that will fix these issues, and I've pored over the manual, but I'm pretty sure I might be too stupid (or word not allowed) to understand what I'm missing.

Just uncheck the "ATC Assigns SID" and "ATC Assigns STAR" options on the FltPlan tab of Config.

This will prevent P2A from adding unwanted SID and/or STAR.  

Dave