For the festival I also used my pair of POS 15"/piezo direct radiators for drum fill (stacked tweet to tweet).
Powered and controlled by: Soundcraft Spirit live 16 channel desk, DCX, DEQ, FX, EQ's etc, 2 x Jands 920 amps (450W at 4ohms pers side) for subs and Drum fill, 2 x Crown XLS 1000 Drivecore amps (212W at 8ohms per side) for tops and Foldback.
PA for the day's purpose was to cover a mixture of Official speeches, school children performances and 3 bands/solo acts and Emcee for the entire grounds. A tall task for a moderate sized PA situated roughly in the middle of the grounds.
Started setup at 4 am. 1 x DR250 either side of the truck trailer (off a 22 wheeler, about 17m/51' long) Subs stacked and V plated in a 4 cab cluster under one end of the trailer. WH8's (and mikes/mike stands) distibuted about the trailer and the small stage in front of it as required. Everything went to plan. Ready to power up at 7.45am (for 8 am start) when the sparky tells me he's reconfiguring the power. Took 7 minutes, powered up, then a stallholders piece of (faulty) equipment dumps the breakers on the shared circuit twice in 5 minutes.

Recorded music on 10 minutes late but no biggy.
The rest of the day ran smoothly.
On to the review.
Subs HP at 40Hz, LP at 100Hz, crossed to tops at 100Hz. FOH tuned with pink noise/auto EQ and not terribly different from my initial tuning trace based on SPL charts from here.
WH8's HP at 100Hz, EQ faders dropped out from 13K. POS 15's HP at 50Hz.
The 4 x T39's (edit: V plated, thanks Harley) kept up to the DR250's, just, without strain on the system. I'm glad I built the extra 2 T39's. Sound wise, the FOH was exceptionally (crystal) clear in the mids and tops and punchy/well defined in the bottom end and there was no "mud" at any time. Volume levels varied from 80db to a max of 114dB (-5dB on the master faders) at one metre (calculated) as the desk and SPL level mike where 20m from front of stage.
The WH8's provided clear concise foldback.
Plenty of fantastic comments (both from the audience/crowd and performers) made about clarity, "great sound" and well heard over a large percentage of the grounds. Estimated crowd 2,500.
And gladly, about nice mixes as well.
All in all a very very good day for a novice who's never owned a mid sized PA who decided his first opportunity to run it was at an outdoor festival.
Lesson learnt, work on foldback gain structure (I very nearly ran out of legs for foldback due to the way I had it set up), otherwise leave it alone as it ain't broke...