Can't say I've ever put a set of MR twins into a board and felt it go any better. Usually on my forehand I haven't liked the amount of release off the top they give.
In your board I'd be trying a set of twins with less overall area. Longer base with a narrower tip like these and a stabiliser to give the hold that you lack on the backhand.
https://www.sanctumsurf.com.au/modii-twinnie-twin-fin-stabilizer-fcs Not expensive so easy to try.
If you put a medium performer in the centre with the MR twins I reckon it will be back to the boat anchor feel.
Going back to a more conventional thruster set up I'd go for a set of Stretch's over an AM2 or Mick Fanning set if drive is what you need.
Should you wish to try some Neo glass Carvers in larges I can post a set down to you to try if you pay for the postage from the Sunshine coast.
Alternatively have a look at the thruster sets on the Sanctum site if you try the AM 2's and they work for you but want to spend less $s.
Thanks man, appreciate the offer for the fins ! legend. But dont worry I can go to the local surf shop and borrow some fins