Thumb size problem

Hi , i love this plugin as it helps me a lot, but i have one problem. Even i did set in media and functions the max size of images, sometimes this plugins generates very large images from dailymotion and youtube. I Need mostly 300 x 250 sometimes 640 x400 but plugin generates like 1024x 800 and more, and then with lot of those size images, site get’s big and slower.

Any solution for this? I did tried with imsanity, ewww and smush it but no luck.

thanks

https://wordpress.org/plugins/video-thumbnails/