How do you use Informix for OLTP?

I am struggling with some Informix issues which I am sure others have solved, or else maybe the people with these problems are using another product. First, checkpoints block all writes, so if I needed to guarantee something like 1 second response time for small insert transactions I can't find any way to do it. Second, since the page cleaners randomly wake up, there is no way to deterministicly tune checkpoints unless the checkpoint interval approaches 0, for example 10 seconds. My LRU_MAX value is set at 1% but my system usually runs 7 idle cleaners and 7% dirty queues. Now granted I am using NT, but it's a 2-way 450 PII box; and granted I only have 3 disk pairs; so I don't have the most horsepower. Am I just out of luck because I don't have enough horsepower? What does a DBA have to do to get some performance? Cheers