So I've attempted a couple of high gravity (1.100+) brews and have ended up with woeful efficiency - in the order of 55/60% - the result of which is that the brews I've tried are obviously going to be nothing like the brews I'm wanted to make. I know there are a couple of improvements I could make in my process. For example, the last brew I mashed for 90 minutes and the mash temp had dropped such that I couldn't get it hot enough to do a decent mash out of 75 degrees. Next time I will adjust efficiency and increase grain volumes but other than that I'm interested to hear from experienced big beer brewers about the particular processes you follow to hit your target SG.