Make sure you get a real FICO score. There are mortgage-specific versions that are different from the credit card versions. (myfico.com apparently gives a mortgage version)

Make sure all of the cards (except one) REPORT zero balance - so pay in full before the statements close.

Then be prepared for an extensive manual review of the application wherein you tell the truth about all the cards with an attitude that, of course, it's not a big deal...

If you can't wait 12 months, then 6 months is better, since the effect of inquiries is strongest in the first 6 months.

(General advice.)