MultiBit already sends with a ridiculously low fee compared to what fees are actually recommended to be these days...
I think the maximum that either MultiBit Classic or HD will actually use is about 50 sats/byte...
Given that the recommended fees are currently 500+ sats/byte... Any transaction you send is likely to get stuck for a while.
There is a reason everyone (including the MultiBit Devs) is telling users to migrate from MultiBit to other wallets without bugs and better fee systems