As with anything, you must define "double predestination" before you can start labeling people.
RC Sproul points out that predestination may be "double", but it is not equal/symmetrical.
It is true, based on the definition of the word "predestination" (a destination you are headed to) that every person is predestined to either heaven or hell. That's true no matter what one's soteriology is. Even for our Arminian/synergists, that is true. Every person is headed to one or the other no matter what one's soteriology.
If a Calvinist claims to believe "double predestination", it may simply mean that he understands this. Or it could mean that God predestines the reprobate to hell, but not in the same way he predestines the elect to heaven.
When he predestines the elect to heaven, it is because God intervenes and positively works and acts to save that man (who would have ended up in hell otherwise)
However when he predestines the reprobate to hell, it isn't because he positively intervenes and acts to force that man to go to hell - the man is already going there anyway because he is a fallen sinner. Instead, God simply lets him have his way and lets him remain in his unbelief and lusts.
Thus, the two situations are not symmetrical because in the one, God actively works to change a man's fate, in the other he simply lets the man do what he wants to - stay in rebellion.
Thus, I believe in double predestination. But I realize that the two are not symmetrical. In the one, God actively intervenes to save. In the other, he simply "gives them over to their desires" which is exactly what Paul said He would do.
How?
You'd make a fine Calvinist, as we don't believe God is the author of sin.