There's always health risks when you're combining uppers and downers. If you don't overdo it, don't do it often, and don't already have some health condition, you would probably be alright. I personally would do a smaller amount of H with the crystal just to level you out. Then do the rest(if you have enough) when your coming down. If you're just really looking for the speedball experience be VERY careful. I've had a couple of friends who got addicted to speed-balling and it really amplifies the trouble you can get yourself into. One last thing of note, I don't know how you can know the quality of H you're getting unless you've already had some in the same batch. Not to discredit what you're saying, but most people don't really know until they get it. You never know when something is going to be cut down again, even if it's a batch you had before. Then again, I guess this comes down to the particular situation/relationship with dealer or higher level of command.