To be honest something like these would be ideal
https://jolla.com/install-sailfish-x-xperia-10-windows/

I dont really need dual boot. it is my second N900 so if I lose Maemo5 it is not the end of that experience.

I assume Leste has functional OTA updates if I make it the only OS for this phone.

I really need to flash it from a Windows PC, my Linux laptop has network connectivity issues I am unable to resolve so it can run Flasher 3.5 to get me back running as I have all the files on USB drive. But to do anything with files from internet is slow process.