Female platies can store sperm.
I'm not sure but wouldn't they have bred by then if they had stored sperm? I've had them for going on 5 or so months now.
So here's my updated plan:
11 Neons
1 DG (researched more into GBRs and they seem hard to keep) I called my local store and they don't have any Plakats unfortunately.
3 Platies