No problem man.
In fact I did some research over the weekend and after looking at your screenpack, I realized exactly how we are going to do this.
Actually there is an even better way to design the entire screenpack in HD without having to worry about problems with the portraits - and that is by using a "custom" HD resolution.
Instead of using 1280 x 720 widescreen HD, we use a custom resolution of 1280 x 960.
This resolution is also called "Fake HD" or "Double Hi-Res".
What it means is that we can double the resolution of the existing screenpack and we dont have to worry about problems with stages.
It means you will still be able to use all your existing 640x480 stages, and also use the same portrait art.
However for me to do this i have to be very careful with the design and the RAM usage when creating HD screenpacks so I need to make sure I know how many stages and characters and musi is loading etc.
Is it possible you can send me your current build of characters and stages (whatever you are using currently) and bgms from the sound folder?
I want to build it as close to what you are using as possible to get the correct feel.
Also there are other reasons to do with the design but we will worry about that later.