The LEI report, out about half an hour ago at positive .1% was slightly better than estimates of negative .1%. Stocks, combined with news that Yahoo and Microsoft are stepping closer towards a deal, are moving higher on the news which is pulling some money out of the fixed income market. If you already have rates this morning, it's not a bad idea to lock as there is no telling if the news will create some market momentum today.
The 5.5% coupon is off at least 4/32nds since last post and we would not be shocked to see the downward trend continue in light of the LEI report. So again, this suggests locking. However, MBS have been tracking well with other fixed income this morning, which has been inversely tracking well with stocks. So if you see stocks continue to move higher, this is yet more evidence suggesting locking.
I realize you might not have rates yet, so when you get them, take note of the stock market at that time (better yet, take note of the 10 year treasury). If stocks move higher or the treasury yield moves higher, yet more evidence to lock. If they hold or reverse course, feel free to float as long as you check back here for updates that may be causing MBS to break it's unison step with treasuries.