Yup on unmaskng, I have a 9" concentric on the MK and it performs well enough and handles flat iron well but does not unmask targets from nails at all. I often use a old cut nail as my break point for junk iron range when coin and relic hunting. The Kruzer it is id 4...... not much wiggle room at all. Actually snagged a Gold Racer and it's all metal dances through iron incredibly well. I also love the imask feature to break up coal and pick through hot rocks. The 56khz is also impervious to the emi around my area so I am able to hunt under transformers etc. Break on that is 23.
Will see how the V80 does in iron unmasking but have a feeling it will be like the legend, apex nox and manticore as they all use same tech and none have concentrics.

Good news is your Fors and my Tesoros are not obsolete quite yet