FireStudio Mobile to Thundrbolt 3 - Higher Latency?

I upgraded my Windows laptop a couple of months ago, and the new one has Thunderbolt 3. I have the Startech Thunderbolt 3 to Thunderbolt 2 adapter, then the Apple Thunderbolt 2 to Firewire adapter and a bilungual cable. It's a faff, as many people have said but it works... but:

Since I've upgraded, I've had a lot more problems with dropouts, and I have to add more dropout protection and add latency. When I do that, it works without dropouts. It happens with virtual instruments and when I'm recording guitar it's close to the point where you notice the latency when you're playing.

The CPU (i7 6700k) is nowhere near it's limit, the cpu meter in Studio One is way down, not even a quarter - the machine is deliberately way over specced (desktop CPU in a big laptop chassis) so that I wouldn't have to worry about this kind of thing. I've got M.2 SSDs and 32G RAM, and I turn off everything I don't need on the PC. Latest drivers, latest firmware, so far there's nothing I can find that would explain why the system would have noticeably worse latency than my old, much slower rig.

The obvious suspect is all those adapters :( Does the Firestudio through the adapters into Thunderbolt 3 have higher latency than when it's coected straight to a firewire interface? If it does it would be good to know, so I'm not chasing my tail searching for tweaks and fixes when nothing will help.

I don't really want to have to go to buy a Thunderbird interface, especially as there's no equivalent of the Firestudio Mobile, but i'm not putting up with the kind of performance I'm getting on such a fast machine.