Today I brewed an APA with a target SG of 1.046, but for some reason my efficiency was off by about 20 points and I ended up with 5.25 gal. of 1.035 wort. I've never had to add DME to adjust the gravity before, so I was cocky and figured this would never happen to ME. In other words, I had no DME on hand, and my LHBS had already closed for the day. I figured instead of an APA, I'll just call it an ordinary bitter, and pitched my yeast.
But it's bugging me that I'm not going to end up with what I had originally planned to brew. I haven't decided if I'm going to do this or not yet, but theoretically, could I boil about .25 lb. of DME in .75 gal. water, pitch the same yeast strain in that, and then blend the two together in secondary? Or even on bottling day in my bottling bucket? The math seems right, but I have a nagging suspicion there's something I'm overlooking here.