I'm the original author of the SR1lm script. Sorry for the delay but I haven't looked at it for ages!
Whichever values the script is generating, it's clear that it's not communicating with the SR1 properly, as the 'uptime' field is zero.
If you could try rerunning with a -d option added to the call, you should get some debug output. This is probably the quickest way of working out the problem. If you can then send me a sample from the start of the run (preferably by PM to avoid clogging the group) hopefully I can see what's wrong.
I'm not aware that there has been a difficulty in indentifying which value is related to which MODCOD. For one thing the values are obtained in a single SNMP transaction.which should minimise problems. Do you have any specifics David?
When I get a chance I'll have a look at using Ernst's equations to simplify the script and compare the results to see if there has been a change, although I'm not sure that there is much of an advantage assuming the the SR1's output is correct. Also I'm not terribly happy about using empirical constants when we have the values anyway, assuming that the SR1 people knew what they were doing. Actually once initial values have been found, the script only samples every 5s by default, or as specified, which I don't think is much of an overhead.