Hmmmm. Cutesy nickname... You could use Sin-chan or Sin-hime, but that's not really much shorter, lol. You could use "Sinny," "Sincie," "Rely/Rellie" or "Cere/Cerie." A few ideas :D. I've taken to calling RenegadeRunaway "Rennie" in PMs, and she already shortened her name to Ren in her bio. We should also create nicknames for everyone else too. What does everyone think?

Crimson Flame: Do you have a preference? "Crim" or "Crimbo" seems like the most obvious, but "Cee-Eff" could work too. Could also use "Mon" like you mentioned, but it doesn't match your username here, lol.
King Kindred: Do you have a preference? "King" or "Dred" could work, or "Kay." 
Role Model: Do you have a preference? "Arrem" or "Rom" might work, or just "Rol/Role."

I think Raistlin is gone, so I won't bother with a nickname for him just yet. These are all, of course, just ideas. No one is obligated to use them. And Sincerely, I'll go read your post shortly :D.