Okay flow rockers are basically clevo type but in two stud sizes.
5/16 pedestal mount - no machining
7/16 stud mount - needs machining
The 5/16 this run the risk of pulling out at high rpm - but this is dependent on your cam size and valve spring pressure. This is something ando gets very passionate about. I’m surprised the mention of double springs hasn’t woken him up.
the 7/16ths are more common and easy to get but need the pedestal machines to take the stud mount. They tend to be more stable but n high rpm scenarios, and then if you’re really serious in running a big cam you need pushrods and guide plates. But this is a serious engine something that sacrifices some crossy strengths ( low down torque) and drive ability for those moments when you can hold a throttle fat and go waaa waaa waaa.
i have a set of the 5/16 adjustables in my xf. It’s efi, they do not fit under the efi cover without an aussiespeed spacer. It’s also not standard efi - eb inlet el ecu with quarter horse.
i could have gone v8 had less hassles but I kinda like how friendly the crossy is. It’s not a fast combo but it’s a great streeter with a Bit of attitude which I’ve learnt a lot from.
Other guys like rob and ando will have their own bit to add to this but hopefully this helps in the interim