I played 1 handed for a long time, but when I switched to index, I did have a hard time. The issue with 1 handing is that it has WAY more limitations speed and combination wise. That, and since most songs now are designed for/by people who play spread, they are significantly harder to do 1 handed because of the patterns. Things like fast rolls are hard 1 handed, harder than any other style of gameplay, for example.
I highly suggest you switch, because I found that as a 1 handed player, my ability peaked at playing quasar 1.2 and Aing it. I switched to spread, and sucked. I sucked for quite some time, but I stuck with it because any song with jacks in it would instantly PWN me 1 handed, and at the time, a lot of sim makers were making things for index players, which tended to have mini jacks, and other annoying things that are hard to do 1 handed. So, I kept at it and within a week or 2 I began to see some pretty decent improvements, and within a month I was beating the crap out of old scores.
Then, I began playing some harder sims, and noticed that there were some things that I was really having difficulty with, mostly streams with jumps in them. Even 8th streams with jumps in them were kinda hard at the time, so 16th streams with jumps were instapwn sections for me. I decided I would try spread and lo and behold, after about 2 hours of playing I was beating top scores that I couldn't even come close to any more with my indexing. I was able to actually beat my score on reality, despite the fact that reality has a lot of drills, which are hard for me to do well with in spread.
After having played 1 handed, indexed, spread, and a couple other styles, such as this:
4
123
1 = left middle finger
2 = left index finger
3 = right middle finger
4 = right index finger
And other things like that, I've found that spread is probably the best technical style to use. There's no extra movement from one key to another like in index, each finger has it's own designated key, which cuts down the length of time it takes to press each key in various combinations, making it overall faster. Each finger is completely independent, meaning that as long as your keyboard supports up to 4 keys, you can do any combination possible without needing to do something weird to press the extra keys. It's easy to learn to read, because the keys are set up to mirror the visual layout of the screen receptors. It's rather natural in that the placement of your fingers is more natural to a typist than indexing would be.
There are probably other reasons too.
I'm not saying you need to change, but it would be a good idea to spend a couple days trying to find a different way, because 1 handing and indexing have some inherent flaws than tend to make some things way harder than they should be.
Oh, and timing wise, my MA is almost never more than 10 x my PA, and I can only AAA things that are about pad 10 footers. Anything above that and I'll likely get a couple greats, because I'm rather inconsistent (I have a hard time keeping a combo and such, though I can get 2000+ combos on a couple songs).