File H1b extension while COS H1 to F2 pending

[rach97gan]

My H1b will expire 10/22, my wife has applied for F1 and will get I-20 for both of us around 8/15, I am planning to file COS H1 to F2 as soon as we receive the I 20.  I have 42 days of H1b to recapture.  If I file H1b extension AFTER I file COS, what will happen?  The reason I am doing this is because I am worried about the uncertainty in COS from H1 to F2 since I had a denied NIW before and I am told that there is a small chance the COS from H1 to F2 will not be approved.  The current processing time of COS is 2.5 months, I may not see the result of COS before my 10/22 H1b expiry.  I am hoping with extra 42 days added to the H1b, I will be able to get a result of COS before my H1b expires, therefore allowing me to take other actions in case COS is not approved.  Anyone know what will happen when if I submit H1b extension after COS of H1 to F2 is pending?  Thanks for helping.