I've built four HT Frames, three HT420's and one HTFPV, I really like the HT420. The HT420 is very rugged, easy to balance so its really smooth to fly. I didn't think the frame made that much difference but after trying some other frames I've concluded that in my opinion the HT420 is about the best frame I've used.
Here's a video of and from the 420. I shot this with a Sony HX9V, which is notoriously sensitive to vibration and the Sony Nex5N with a CC controller.
https://vimeo.com/45625352
Also, although its been quite a while since I've needed any support for frame related things, Tom from Hoverthings support was excellent, he was very attentive and easy to get in touch with. I have not tried the flip frame but I thought I would share my experiences with the HT420.
Good luck and let us know how it goes.