Frugel Horns with Foster FE163 drivers

Hey Folks,
I am going to be building a set of frugal horns for these drivers. I have been in touch with Dave D. and he has a set of plans for them. I'll be getting them soon. I will keep this thread updated as I go along with pics and questions.

For now I do have a few questions. My limited reading has me suspecting these will be some really good horns with the exception very high and very low roll off. The low I think I can deal with using a good sub and filters. However, I am not sure of the highs. First, does anyone have a guess asto what frequency I should look at for roll off? 8K, 10K, 12K, ???? Next what spl would be a good level to mate to the horn, 95db/spl/watt? Lastly, Dave reccomended a horn tweeter as best suited to match the horn. Any reccomendations?

My drivers are rated at 5w RMS or 10 peak, so power is not an issue. I will likely run these with an el84 pp tube amp - capable of 5-7 watts RMS clean power.

Thoughts anyone?
mark