While I wouldn't recommend mixing Scotch and Bourbon per se (worst of both worlds, as I see it), a few drops of either won't hurt the other.
One thing about a flask... even if it has a brand name on it, everyone knows you filled it with something and they don't know what. You can go cheap, and swear it's high-priced stuff. Or you can fill it with the best you've got and just smile when whoever you're sharing with says, "wow! that's great whiskey".
OR...
You could buy up a case of cheap flasks and have your name etched on 'em, then fill one with Pappy or Stagg and tell folks it's just Jim Beam White, but the secret is the flask. "Why I just happen to have a couple of these I could let you have, for a price. Now, Y'know you gotta leave th' whiskey in the flask for at least a year" (that gives you plenty of time to get out of town)