I believe you are looking for the testexec.lite.longMsgLen property. testexec.lite.longMsgLen allows viewing the full text of long responses. Set this property to the length of your longest response in the local.properties file. Run a test, capture what you need, verify that the correct response is indeed being sent back, and then comment out the added line in the local.properties file to revert to the default length which is 1,024 bytes.
The reason one does not want to leave this on all the time is that it can negatively affect the performance of the VSE.
As an alternative, try looking in the vse, vse_matches, or VS_serviceName log files for the full incoming request. I have also used the built-in _logger inside scripts to dump requests into the vse log.