canfield
BJF, you have been experiencing good luck, or positive variation as some would put it. Competent players will have many different experiences, even betting in similar fashion etc. I personally have had good luck, with the occasional hammering over several hours. However, I have never had a truly prolonged losing streak. I know other players who play as well or better than me, with excellent discipline, who have gone for long periods of just getting creamed. Trust me, if you keep on playing, you will hit a period when it will be so bad that you will question the game, your skills, or wonder what mysterious cosmic event has caught up with you.
Regarding the system for sale, it is called the Master System. You are already playing the Expert System. The Master System is a multi-level count that I think is also known by another name, but I don't remember what it is or what the card values are. I can tell you that its not worth $250. No count system is. If you want to play a more powerful system with ace side, and you specialize in SD, go for Hi Opt II. It is only 2 level and is just as strong if not stronger, than the 3 and 4 level systems. You can buy Hi-Opt II either on this site (I think) or on RGE21. The best thing though, is to play a system where you make as few mistakes as possible and don't get tired as fast, and that you can play a little faster.
I also played Hi Opt II for several years, and it was excellent, but I switched to Hi-Lo when I started playing more shoes, as well as not playing as much. Hi-Lo works well and is extremely easy. For single deck, I carry an ace side to make up for the loss in playing efficiency, which is more important in single deck. I use the ace side to improve the insurance bet correlation as well as other close strategy plays. This makes Hi-Lo just as good as the Expert, but probably a little easier.
Regarding betting if you are spreading to 4 greens, I would bet 4 greens at an ace adjusted true of plus 3 or more. I personally try to make my top bet at an equivalent true of plus 2. This will increase your variance, but it makes it easier to more consistently get your top bet out when the count is higher. On the other hand, betting with the count to a max of 4 has probably helped you from having as much negative fluctuation.
Unfortunately, the apparent win rate you describe won't last! You are doing far better it seems, than even a perfect computer sim will do over the long run. So appreciate and remember the good ride you have had, and hang in there when it goes the other way. Have fun, bjdavid