Since 30% of your credit score is credit utilization, having large balances on your personal cards when the statement closes will cost you.
How about while you're shopping for a mortgage, you pay them off in the month you spent the money? Keep it up a full month (for all the banks to report) and you should have a CS jump.
I think, only a small, personal-type bank will override the CS. But talk to a mortgage broker for firm thoughts.