Thanks to some helpful advice from Cafe members who chimed in on my thread about lavalier micing an F4, I bought a DPA 4099 miniature cardioid instrument mic last week. It is expensive, but it is hands down the best mic I've ever mounted on my mando. Over the past ten years I've tried almost every mic/pickup I could lay my hands on, and had settled on an Audio Technica ATM 350 with a Fishman bridge transducer into an Aura modeling system, but the DPA is now my fave mic of choice.
1. The hypercardioid pattern of the mic lets you use the mic in the monitor with almost no risk of feedback. I did a gig on a loud, echo-heavy stage on Saturday night with a stage blend of 50/50 mic and Aura, and I 'd never been able to get away with that much before. I might have been able to use more, but we had a rushed soundcheck and i was already amazed at how much better my mando ( a Hilburn F5) sounded in the monitor that I didn't push my luck.
2. The gooseneck clip works beautifully. I can even mic my F4 attaching the mic to the upper point and get a natural feedback-free sound with the mic high enough off the oval hole to stay away from my hand, and not be too woofy from being too close the the hole.
3. The mic has a very focused, clean sound. It seems "sharper" than the ATM 350, not brighter, but more detailed. In live recordings I've done with the 350, it picks up a lot of what's on stage; I'm fairly certain the 4099 will have less bleed.
I've used many different freestanding mics for stage work, but in the swing band I work in now I need to move around. Nice freestanding condenser mics, with the exception of the Shure KSM9 and a couple others, are also prone to feedback when you try to use them in the monitor. The 4099 solves the problem of having a great sounding mic that lets you move with it. Since i was able to hear the subtleties of the instrument in the monitor like never before, I felt I played better and more relaxed , and the other band members confirmed this.
I bought my model with the guitar gooseneck, and bought the violin/mando clip as an add-on ( $60) If you're micing an F-hole mando, just get the violin model. The guitar gooseneck is longer and better for the F4.
Thanks for the suggestions.