I installed this during my build without issue. It does provide a very clean roof line. Having done the composite tailcone instead of aluminum per the drawings, I can't speak much to the effort or time difference added, but I can say it was pretty straightforward to do and I spent 41.1 hours including the shelf construction and finishing the cabin-tailcone boundary with micro. I imagine someone more skilled at composites would move along faster.
Anecdotally, with the tailcone epoxied around the top of the cabin along with the normal rivet line at F-1006, you have more points of connection for the tailcone roof vice the one that aluminum would have the one bulkhead per the KAI; it's a solid installation.
I made small shelves with Divinycell H80 overlaid with 2 layers of 120-38 and aluminum base plates screwed to plate nuts I installed on the divinycell flanges; a larger one for my three GPS antennas (between F-1006 and 1007) and small one GMU 11 (farther back just forward of F-1008). Don't forget a nice ground plane connection to the airframe.
I'm happy to report that with my RV pulled outside of the shop, the GPS antennas are fully operational with all available satellites picked up. I also have my ELT mounted (vertically per the TSO instructions) internal to the tail cone and it tested well too.
I don't have my wings on yet, but no magnetic influence issues with the GMU in that location from the elevator, trim or anything else turned on or moving. I'll need to retest once the wings are, hopefully later this summer, but I don't expect a different result.
ShowPlanes did a very high quality build with a perfect fit; I can't say enough about Bryan Milani's support (and willingness and patience to answer my questions, along with talking me through using divinycell...I'm not a composite's guy and had never heard of it before this)
With ease of installation, very clean lines without all the antennas on the exterior, and just plain aesthetically pleasing, I highly recommend doing the composite tailcone cover.