The message "Request entity too long" error message indicates that the request you are submitting is larger than 20 KB. The reason for the larger size is usually that the request offering contains a large bitmap icon or large number of prompts.
The upload size in Windows Azure Pack is by default set to 20 KB, but it can be modified by running a script. Please see the section “File upload – Required Configuration” in the Deployment Guide for instructions.
Try to increase the size to 200 KB as a first step.