Welcome to WhitneyZone, Michael. How many slots are on your permit reservation? For you and a friend, you need two. For a third person, your permit must be for three people. How many does your permit say?
Unless you are a slow hiker, it is possible to ascend the MR in 6 hours, especially with a day pack.
If you really study the Mountaineers Route information, you should be able to do it on your own, starting up the Main Trail just before first light, and then starting up the North Fork as dawn breaks. If you have memorized the route, you would have plenty of time to make it down the main trail before dark. Here's the MR info:
Mountaineer's Route info links withinEdit: Mike replied that he has 4 slots on the permit.