Congabebe,
I have had similar difficulty. I like the idea of the conga feet. I bought them for my segundo and tumba. I hold my quinto between my legs. I have found that once I get set up and my drums are where I want them, things are okay. However, the adusting time is a pain.
Before I got the LP rubber feet, I used some short dowels to tilt the conga and tumba a little bit. This made the drum a bit unstable, but I found that if I played with some control and if the dowels were not too big in diameter, this worked well. The same goes for the conga feet, which when placed correctly, leave my drums more stable than they were on dowels.
I think my biggest problem with raising the conga and tumba specifically and my playing in general is that I try to play too hard. I have learned to rely more on amplification and it has saved my drums, my hands, and my ears (when practicing). It has also allowed me to relax and play with more finesse, speed and endurance.
Sorry about the little personal aside. All in all, I like the idea of the conga feet. I'm not going to give up on them yet. They could use some design impovement, but that would make them cost more than ~$15 per drum.
I guess you get what you pay for. ???
That's also what you get when I put in my $0.02...
Zach