Nick Gammon's Hex Fixed Name uploader - Problem with Fuses on AtMega2560

First of all, hi to everybody, I hope that I will be of help in future. To be short:
I made my own board with AtMega2560.
Second of all, all thanks to Nick Gammon, he made my life really easier. Really. Great guy with some great codes!

Everything is fine, I upload bootloader (with Nick Programator), work with Serial, uploading sketches. Everything is great.

Put then, I tried with SD HEX Fixed Filename uploader. First time everything was great. But only because I used the same board I used to try out bootloader programmator. It clears the low fuse, and now, with fresh board, what do I get:
It was very weird. It took me time to see that uploader works, but sketches are very, very slowed down. Immediately i understood that I might not be using the correct clock in fuses. My board have 16mhz clock. But sketches were slowed down.
If I use, HEX FIxed Name uploader directly on new board, it just copies fuses, wrong fuses. This is the new board, without touching before the HEX fixed Filename uploader:

Attempting to enter ICSP programming mode ...
Entered programming mode OK.
Signature = 0x1E 0x98 0x01
Processor = ATmega2560
Flash memory size = 262144 bytes.
LFuse = 0x62
HFuse = 0x99
EFuse = 0xFF
Lock byte = 0xFF
Clock calibration = 0x5A
Bootloader address = 0x3E000
Bootloader length = 7474 bytes.

And this is the export from the board with Clearing 'Divide clock by 8' fuse bit and fixing low fuse setting with Nick Programator

LFuse = 0xFF
HFuse = 0xD8
EFuse = 0xFD
Lock byte = 0xEF
Clock calibration = 0x5A

After this, on the same board, everything is working fine. Problem is with LFuse (i'm 99% certain) because 0xFF means that only then is uses external clock. With this LFuse = 0x62 I do not know what is using, something internal and slow, probably...

Now, the problem. I can remove fuses if I use Nick's Programmer or "Hex File Uploader". But, with "Fixed Filename Hex Uploader" it won't work. And I really need it to work with Fixed FIlename from SD card because I need automation.

So, anyone knows where to change fuses in that script? I think I will find out, eventually, now I'm looking at the regular Hex File Uploader, the function where you change that. It will be some trial and fail, but I thing that I will manage. Anyway, if someone knows how to do it right away, it would be awesome. I hope that Nick Gammon will see this. :slight_smile:

Ok, now I can confirm that problem is definitely with the Low Fuse, when I manually set it up with Nick Gammon's Hex Uploader to FF everything is working normally. Now I got it back to 0x62 so I can find a way to do it automatically with Nick Gammon's Fixed Name Hex Uploader.