No, you can't. I'd say an average member can move up from Jr. Member pretty quickly if they're a decent writer or contribute stuff that's significant, but once a member reaches Full Member rank, it starts taking a much longer time to reach the next rank (assuming their posts aren't prolific and well above average). Bumping up the number of merits sent per post even by 2 probably wouldn't have much of an effect if a handful of merit sources did it, which they probably won't.
You're right, I experienced it even though I actually got full member rank when the merit system was introduced. What I understand is that everyone has their own standard of spending the sMerit they have each month, and since each user has different abilities and skills when posting then the amount of merits they will get should vary depending on the quality. This implies that the merit system is working as it should and each user doesn't have to spend years climbing up the rankings if they are really quality posters.
Of course that a user like me would have a harder time earning more merit because I probably haven't met many of the standards most merit sources expect. I'm waiting and I'm trying, but I can't get everyone interested in submitting merits because maybe the quality of my posts isn't what they expected. I'm just sure that sooner or later I too can become a Sr member, but I don't think I have to complain about why I had to wait so long to get one.