I wouldn't think a 1" LMB(or once grown to 2") will be able to eat a 1+" FHM. If you put the FHM in now, they'll have a chance to spawn before being predated.
I was at a fish supplier that had a tank of small 2" LMB. He said watch this. He took a one inch minnow (possibly larger?) and dropped it into the tank. It was taken immediately. Perhaps this was because of ravenous fish in a tank situation, but I saw it first hand as being possible.
I do agree putting them in now is a good idea, but stocking any later is not very beneficial.
