i had my set of curves on my 2011 and when it came to the loose snow they pushed in the corners with good carbides and i have that sled set up for ski pressure. with the mtx skis and my prefered carbides, it goes where i point it unless it is sugar snow. run the same set up on my 2016 apex xtx and it is almost as good in the corners as the 11. tip up rails on 11 make a noticeable difference. got my gf to try the 11 with the curves and she did not like them. had to put the mtx skis back on it.
as i have had the curves on my eps apex, the rubbers they offer do not fit right. i ended up using a chunk of 3/8" belting in the bottom of the mount pocket with the stock rubbers and they start fine but need about a 1/4" shim added to the rear side after about 1000 mi as they would hang tip down when in the air. had the same issue on the 05 rx as well.
as to putting mtx skis on it, it depends on how agressive a rider she is. they can be installed with the 2 bolts (90105-10410-00) and nuts (95607-10200-00) using washers to take up the extra space between the spindle and the ski if she is not too agressive.
if she is or some one rides the sled that is, i reccomend getting the sleeves (2 of 90387-10036-00) and spacers ( 4 of 90387-16013-00) as the bolt has been known to break on hard hits with the washer method. i did one with washers and broke it. converted them all to full hardware and no problems since.
the nitro and phazer mtx skis are the same as the apex ones. i did have to get one set new as i could not find a used set and as i had older sx and rx sled skis hanging around, all i had to buy was the bottoms as i already had the loops and bushings i needed for them. i still have a spare set ready to go in the trailer or garage when i need them.
other than the rubbers, the other aftermarket skis that i have tried all just bolt up with the supplied hardware.