Oh, we have been. It runs at about 7 (spreadsheet) rows per second on our local boxes and 1.9/sec on a VM which is the
test server. Our users are rejecting the facility because it is too slow. I was trying to figure out what 'reasonable' means in this case. Basically, we didn't know when we should give up and try something else.
Since I posted we got some political pull and were able to get the code onto a production server. It runs at about 17/sec there which is very acceptable.