I don't have a lot of time at the moment so I'll try to cover as much of this as I can real quick and then if I have time later, I'll come back to it.
I started out around the 150-160 lbs when I came to HST, at probably about 6% bodyfat maybe. I was naturally very lean and also very wiry so I had the whole "eight pack" look and everything. I was taking protein shakes and creatine prior to learning about diet, but had made almost no progress. I had no bodyfat to lose and my body measurements never increased noticeably. I did gain strength during that period though. Perhaps if I had started out with some bodyfat, I might have made some gains due to newbie effect, but I doubt it. It's worth noting that I was always very athletic and active as a child, I used to do pullups, dips and stuff like that for fun so I wasn't coming into weightlifting in a state where I was a sedentary person or anything like that. This could have had an effect things for me, possibly.
Originally Posted by Explosions in the Sky
My first bulk was probably 3-4 HST cycles, I believe. I ended up around 180 lbs at the end of the bulk with some fat gain but not a lot. I did make some mistakes, such as freaking out when my abs turned into a six pack and then a four pack, stopping my bulk and beginning a cut, then freaking out halfway through the cut when I thought I was losing all my muscles, so going back to a bulk. This is a common mistake and can destroy your progress. I've known more than a few guys who let their psychological problems get in the way of their progress. Stick to the plan and don't change things just because you think you are getting too fat or losing all your gains during the cut.
2) What gains did you achieve after your first bulking cycle?
I strongly feel that a bulk should last at least 3-4 months, ideally around 6 months. My best progress was when I bulked for 6 months or more. The thing you have to do, which becomes critical when bulking for longer periods, is to manage your weight gain carefully so that you are not gaining too quickly. By manage weight gain, I mean that you must count your calories and stick to your macros. Increase calories as weight increases.
3) How would you structure a optimal bulking cycle? Bulking for 8 weeks (1 cycle), then cut? When do you stop bulking? What would speak against bulking until I reach the desired muscle mass? Bulking for 1 year and then cut would result in more muscle gains than cutting after 6 months and again bulking, wouldn't it?
It isn't a great idea to bulk up too far beyond 20% bodyfat simply because eventually your body begins to produce new fat cells instead of simply storing calories in your existing fat cells. Probably want to avoid that. And of course cholesterol, blood pressure, etc all go south as you gain more fat. You don't want to have your body in an unhealthy state for too long.
Ideally no more than 15 lbs and no less than 12 lbs.
4) What would be a realistic weight gain over 1 cycle (8 weeks of HST) when taking in about the 20x BW in calories a day you recommended (for a rather ectomorph person like myself)?
I didn't quit fullbody workouts until I began to have trouble breaking the 220 barrier without getting too fat. I had to increase volume to be able to go beyond 220 without becoming a fat slob, and the only way to do that was to split things up. However, the first modifications I did was to start using alternating workouts and this was probably around the time I hit a 425 lb deadlift. Up until then, I did squats and deads in the same day, but after I got over 400 on deads and 300 on squats, I noticed I was getting sick all the time and just generally felt like crap most of the time. I do not think modifications other than alternating workouts are necessary until you are at an advanced strength level. One mistake a lot of people make here with HST is using tweaks for advanced users too early - which basically means using too much volume because almost all the advanced tweaks are just attempts to increase the volume so you can still grow without compromising recovery. I feel you should do enough to be growing steadily and that's all. This is assuming size is your goal. If your main goal is strength or something else, then that is a different story.
5) When did you start to make changes to your HST-workouts, i.e. like changing rests between sets, switch from full-body to splits etc?
Squat - 485 lbs
Bench - 315 lbs
Deadlift - 635 lbs
Total - 1435 lbs