pt-mext feature request: offset and number of samples

Very often I'm using pt-mext to analyze mysqladmin extended output gathered by pt-stalk which has 30 1s samples and unless I cut the output, it's not very nice one to look at. I wish I could tell pt-mext something like:

  pt-mext -r -n 3 -o 5 -- cat mysqladmin.txt

and it would start at the 5th sample and return output for three samples only.

I wish more things, like tell pt-mext to use 10s iterations to give me three columns with 10s between each sample (it could "guess" the time between samples using Uptime in the output of each sample), but for starters, offset and number of columns to return would be absolutely awesome.