Eligibility for ILR - Continuous Period

Hello - I am looking to understand when I can apply for an ILR. My details below:

Mar'11: Entered the country on Tier-2 ICT
22-Jun-2011: Received the Tier-1 General visa
03-May-2013: Extended visa for 3 years until 03-May-2016

Based on the other discussions, I understand my stay on the Tier-2-ICT will not count for the 5 year period. (since it was issues after April-10)

I am specifically concerned that I may have extended my visa too soon. Assuming that I am eligible to apply for the ILR 28 days before the 5 year anniversary on the Tier-1, I would be eligible around the 25th of May-2016. However my visa expires on the 3rd of May.

Any suggestions on what I can do to make up for this shortfall of 20 days? Can I submit my application sooner?

Thanks for your help.