There are a variety of tools that can be used to build an EDID block that can be accepted by the PiCapture HD1. One that we have used successfully is the AW EDID editor: http://www.analogway.com/en/products/software-and-tools/aw-edid-editor/
You may need to manually build the EDID block that you need, using the values you are able to extract from the Monitor you are basing it on.