Thank you very much for your reply, Neil! I downloaded the patcher and did patch MapInstall, it seems that BaseCamp was already patched (or at least the patcher says so). But the only result is that now I can't see my two USB drives (both with Garmin folder on it), I could see them in MI before patching it. The other thing is that this map which size I want to reduce is an .img file, it is not a PC install version. So the question is the same: can I somehow reduce the size of this .img saved on the 1st USB pendrive and send it via MI to the 2nd one?

Thanks again