depending on what you what you run your din at, which i would imagine would be about 9, the 816 would be fine. you could also get the 614 since those would also be withinin your din.
as for the new salomon sth series, the sth 12 is a z12 with a reinforced housing and a stronger metal track. the sth 16 is a 914 with a metal toe pivot mechanism and a super strong track. the sth16 seems thike a very good choise for you if your din is within 9 and 16, if it is not, i's say fks 120 or deadbolt 614/816. the fks 120 is about .4 lbs lighter than the deadbolt and is super strong and safe. the reason i would reccommend the 120 instead of the 155/185 is because the 155/185 lack a vertical releasing toe, which may be nice in the park, although the din on the 120 may be a bit low.