Advice on feminized breeding after second and 3rd generation..


My situation..
I successfully crossed ochisel with grandaddy purp..
I used coliodal silver to force Male flowers on an ochisel plant collected the pollen and pollinated grandaddy purp...
Ive named my strain Bluuchisel..
I now have 2 extremely frosty phenotypes that are also purple..i forced a sister of the two that was also very frosty and purple from early on to herm with colloidal silver, collected that pollen an now pollinated my two current girls...
From what i understand my first generation Ochisel×GrandaddyPurp were f1 now im creating f2 by selfing or inline concidering adding an additional 3rd strain possibly non feminized so i can begin to have a true stable strain and a feminized version...basically i guess id like to know should i introduce my 3rd strain into my gene pool now or or later...should i pollinate my f2 with the new strain or waite for f3 or f4...the strain im introducing is also purple but very high in thc so im not worried about loosing my purple phenotype...any advice or knowledge would be appreciated..