A possible technique for high gravity

So I made a molasses imperial stout recently that I think turned out really well. The biggest problem I had with it was a massive blowout that made a mess, and all told I had a gallon and a half or so that blew off.

I thought of a technique that might help with this. If people could let me know potential problems or if they have tried this and what their results were I would appreciate it.

Would it work to brew up a relatively small amount (say 3 gallons for a 5 gallon batch) of lower gravity wort, let that ferment for a bit, and then add 2 more gallons in stepped intervals of higher gravity wort to get the right OG? I figure this would reduce the yeast stress as well as helping to minimize blowoffs.

I think that would actually create a larger problem. A) yeast that are active are much more likely to create a VERY large krausen, like adding more wort after a starter has finished. It'll BLOW.

Also, the more times you open the fermenter to add the wort, you increase your risk of infection.

My opinion is you get some fermcap to control the krausen.

I don't see any huge problems with that method. You might have to do some extra calculations to adjust IBUS in the original wort so you end up with the beer you intended. Will it prevent blowoff, who knows. I incrementally fed the 10-10-10 beer with 1lb of sugar boiled in 2 cups of water repeated 3 days in a row once the gravity of the original beer reached ~1.030. It didn't blowoff, but I was also using Fermcap and fermenting in a 7 gallon bucket.

Just get Fermcap-s and save your self all the extra work.

I can't speak from extensive experience with fermcap, but my barleywine in the last 10 days went from 1.109 to 1.028 with an inch of krausen and nothing in the blowoff tube.

I'm not real keen on adding chemicals, If this idea wouldn't help I may just either get a bigger fermenter for big beers or make smaller batches.