Tim, I too have an ARC sump...I tried the splash test and got very wet! The bolt in baffling is now in the bin...
Actually in reality it's waiting for me to modify it
I intend to make a bolt in baffle similar to the centre of the Lateral Sump...or buy a Lateral sump if I get bored trying to make it work and still fit around the HKS headers, I was lucky and got an ARC for 360 quid new, here in the UK