15 inch rear loaded horn

Hi everyone,

I'm planning to make a rear loaded horn with my 15 inch Monacor SP-38/300NEO speakers. However I have some concern by the design, since I yet haven't encountered a horn this big anywhere on the internet (without having an infeasible design). And also since this is my first horn, I have some further questions:

Is it possible to make a efficient horn out of a 15 inch speaker?

Since i can't find any design plans, is it possible to scale up an existing horn enclosure? i.e. this fostex plan (by a scale factor of approx. 2): http://www.fostexinternational.com/docs/speaker_components/pdf/recom_enclose/206e_enclrev.pdf

I can imagine the speaker is producing a lot of pressure within the enclosure. Should I be worried about the well being of the speaker cone or the pressure chamber?

If any of you can recommend an alternative speaker plan, please be kind to send it my way.

Thanks in advance to all of you!