Doug,
If your rig can carry it, hanging a 24-240 on that a7 makes for some powerful imagery. For general carry work I’m still using an a6000. A bit limited over the newer stuff but I’m used to it.
At this stage, I'm still drooling on the A7Riii, haven't laid claim to one yet. Kinda waiting for the A7R iv to be announced or released so the R iii will take a dive in price.
That would be an impressive lens, not sure how strong you could set the lens for clarity, although not a power zoom so you'd need a servo & ring if in-flight zoom or racking was desired. The M600pro & RoninMX could carry the payload, the R-MX main improvement increased payload and a full cage compared to the R-M along with the multiple extension rails & balance weights. The R-MX was designed as a compact mount for the RED & Lenses.
I'm playing with different damper mount compared to the stock plunger style. I like this one, but pricey:
Upgraded wire damper mount for DJI M600 | eBay
Nice dampener, each wire coil rated at 1.5kg, total of 12kg > 26.4 lb total capacity so plenty spare overhead, Tunable to payload so not to overly stiff. The carbon plate makes the mount adaptable to multiple AC mounts, looks to be adaptable to the SW1000 Octal I'm customizing for load, taking it from a 15" to 17-18" Octal & upgraded to E1200 TPS (4216 motors). The Dampener Mount actually helps reduce the multiple mounts and reduces overall weight.
I've bumped into a guy that uses a A7Rii and 16-35 f2.8 GM with a RoninMX mounted to a Tarot X4-X8 Octal with 17" push-pull props. The 16-35 is a hefty 680g, the 24-240 is porky 780g (1.7lb). Plus the counter balancer weight on the rear, would be a package.
For aerial, that is a nice part of the A7Riii... it's smaller & lighter than most DSLR's. At 657g compared to a D5 at 810g. Saves on counter weights and allows more weight on lens.
Pat, have your slide handy, for rough estimate... how much lighter payload is the Oct with 18" compared to Hex with 21" for lift capacity. Not calculating for the motor capacity, just the Oct dish vs the Hex dish, considering the 21 has a substantial larger cord section on blades.