got gba mother3 cart to hold saves with lesserkuma's web patcher tool

save patcher github

seting the save type to Off-spec 512K/1M FLASH worked for me.1m flash(128kb) also worked.
when saving the screen hangs for a bit, looks frozen but the saves work.

dumping the gba cart back to the computer i couldn't save in mgba in castlevania. the fix: use the unpatched rom with the 1m flash (128kb) save backup. fixing saving on the mother3 cart breaks being able to save in the emulators everywhere else so just copy the save and use that with the original rom