savsender problem

I've recently started using savsender with my copy of Pokemon Diamond. I can send my 512 kb size .SAV from my R4 diamond rom to my legit diamond cartridge with no problem. However, whenever I dump the legit cart's .sav file onto my PC, edit it, and try to send the .sav back to the legit cart it does not fully send. I think this has to do with the legit card's .sav being slightly below 512 kb, since they are usually sizes such as 506 kb. I also noticed when I open the legit cart's .sav in pokesav, it says "256kb mode" instead of 512 mode, and when i try to convert it to 512 mode, it makes the .sav exceed the 512 kb size. Is there something I am doing wrong? Is there some way to pad the legit diamond cart's .sav to make it 512 kb? any help would be appreciated, thank you.

also, if this question is better suited for the Pokesav stickies, feel free to delete this thread and I'll ask in there.