Lower steep/mash temp (148-150) should get you a lower dryer gravity
Add belgian candi syrup before the boil, taking kettle off heat. Another clone i read used D-180.
Add DME just before boil to avoid boil over.
Yeast Temps: Style suggests starting an abbey yeast at 64f up to 68f for 48hrs to minimize fusels. At 1/3 sugar break move it to 74-78f. The yeasts could increase to these temps on its own also. This is something I will attempt by moving out of my basement to warmer rooms at about 1.046 gravity or sooner. Update: Mine took about 4 days to hit 1/3 then I moved it to a 70f room.
Wyeast 1762 is supposed to be the Rochefort Yeast. White Labs WLP540 is also Rochefort. Other alternatives; Wyeast 3787 or 1214
Mount Hood is an Alternate for Hersbrucker hops with a higher AA. Reduce by about half. From .5oz to .2 oz. You could instead remove the 60min Styrian. This would keep the IBUs from overpowering the style.
Take note of higher priming sugar. Style suggests higher volume. 2.5-3 vols
Bottle condition recommendations are longer. Minimum 6 weeks, but better at 2 months.
Update: Fermentation smells like banana about 7 days in and after I had moved it to a 72f room.
Update!: This recipe works! It taste near close to a proper Trappist Rochefort. After 6 weeks aged I smell banana, its strong but sweet covers it up, its a perfect dry. Letting it age took the edge off.