Harborside is one of the more difficult exchange in the Starwood system . The earliest you can do a Staroption exchange is 8 mos. out, so at 7 mos. out, others have had a whole month to make exchanges ahead of you.
Best Practice: At 12 mos. out, reserve your home resort week as a backup. At exactly 8 mos. out at 8:59 a.m. ET, call and see if the exchange you want is available. If it is, you can cancel your home resort and reserve the exchange. If you first choice isn't available, continue to call Fri., Sat., and Sun.
Added I just noticed that you said "Spring Break" - holiday weeks are especially difficult to exchange into, but if you use the "back up" procedure described above, you don't have anything to lose by trying!