The AY service HEL-DXB is one of their charter type specials, operating one class sub-Y only (28 inch pitch if I recall correctly, on a 757 -- really hellish). These planes are normally used for 3 hour flights to Spain; do you really want to use you AONEx sectors for this? The rules haven't been changed to exclude them, so you could do LHR-CAI or LHR-DXB but not both, and then as many HEL-DXB as you wish. Of course you get Y status credit and mileage bonus, there is no allowance for voluntary downgrades.