Dear Sir,
We are using FMC700 for our KC705 because all our boards are compatible with a VC707. We brought general FMC support at time only ML605 was existing. Then we extended the support to VC707. Later when the KC705 was released we discovered that what Xilinx claim to be a HPC connector is a LPC+ connector in fact.
On the VC707, FMC125 can be used almost fully on HPC1 but there is one exception, "SYNC_FROM_FPGGA" this one is only available if using an FMC700 but this is the only feature to gain in using FMC700 on VC707. HPC2 does not alow a full blown FMC125 to be connected. One channel would be missing typically.
Your safest path towards your results would be using FMC125 on VC707 HPC1. We do have an out of the shelve reference design for this configuration.
I hope the information to be sufficient!
Best Regards,
Arnaud