Now that I've spent a week with the Mk1 springs in place there isn't enough of an improvement to call it a day. Next step was to modify the Mk2 springs so that they were 100mm across and so that they didn't lift the pads quite as much, basically make them like the Mk1 springs. It was relatively easy to do by hand and I fitted brand new Mk1 pads while I was at it.
On a direct A-B comparison to the Mk1 the sound is much closer now with the A/Mk2 a bit more forward and the midrange a wee bit colder. There is still some honk but only time will tell if I can live with it or not.
I also compared the Mk1 and Mk2 earpads while I had the phones open. The new leather used on the Mk2 pads is indeed very nice unlike the Mk1 units they aren't all leather. The lip used to hold the pads to the phones is now made of vinyl which is much looser with even less tensile strength. This makes the phones easier to assemble and the pads deeper but it's a clear compromise over the snug fit of the Mk1 pads.
The new pads are stiffer then a brand new set of Mk1 pads (possibly to make the last longer?) and foam construction and materials are different. The angle of the pads is also smaller on the Mk2 compared to the Mk1.
I will now run them like this for another week to see how it is but the next step is far more drastic, a driver swap between a mk1 and my A which is something I'm not looking forward to...