The "Extras" zip file used to enable sideloading of apps on the HD/HD+ is the same for both devices.
What's different is the "image" file you use to prepare the CWM SD card. They are different files, depending on which device you have. I used Penny's links for that file for my HD, however as explained earlier in this thread, something went wrong with my SD card. So I used the alternative method for preparing the CWM SD card which I think is actually easier. With the alternative method, it is the same procedure to prepare the card for both devices (unlike the imaging method).
It's really easy. It is explained in the link below:
http://forum.xda-developers.com/show....php?t=2062613
You only need to read the first post, parts #1 and #3 for how to create the CWM SD card and use it to install the "Extras" on your HD or HD+.
If you want to stick with the imaging method, then you have to prepare a new CWM SD card with the image file appropriate for the HD. If you go to the bottom of the first post on that thread, it is currently the 5th download file listed under the "Attached Files."
--Pat