gallon boil vs 4 gallons

I got my cider out of my primary and finally decided to go for my first batch of brew. A friend of mine helped me make a few changes to the original recipie but when it came time for the boil I used the 4 gallons the original recipie called for. I have a 5 gallon pot and I tell ya what, 4 gallons in a 5 gallon pot doesnt give ya much room for stiring or all the foam that I got.

Would lowering the amount of the boil to 3 gallons next time do anything wierd or would it not make a difference at all?

If ya need to know more specifics I'll add them in later, trying to get this batch to cool off and figured since I had the wife watching it so I could have a smoke may as well use this time to ask ya all

In general you want to boil as much as possible, but most extract brewers boil 2.5 to 3 gallons. The main difference is you won't get quite the hops utilization.

Boil about 3 gallon. If you can take 2 gallons of pre-boiled water put in frezer as you start your batch pour this into your fermenter will help you cool down your wort quicker which will get you closer to your yeast pitching temp.