Need different size for RSS thumbnails

Currently Gallery only allows one default size for thumbnails. Is it possible to add a second size of RSS images? Similar to wordpress which allows multiple thumbnails. Any available mod that enables this functionality?

Use-case: RSS feeds are being used outside Gallery with different thumbnail sizes. Scaling them image using width/height attributes works but decreases your google page speed score and also increases site load-times.

Any thoughts?

Thanks,
Mick