Not to change your decision but two things to consider.
1. Getting out 9 months earlier in this environ might be worth lots in seniority. Also are you sure you will be passed over cause if you promote then your plan is foiled.
2. You can join selres and will surely promote if you participate but when you reserve retire they will deduct your sep pay from retirement albeit interest free so it's like an interest. Free loan.

This case makes the biggest argument for defined contribution retirements for military as why should 11 yrs of service be worth nothing but failure to promote is?
Luv