I would get on the Facebook groups for R&M and for cargo bikes. This forum is great but it only has a few cargo bike riders. Cargo Bike Republic has over 13,000 members The Riese & Muller Cargo Bikes group has 3000 members.
Insofar as generally on that bike, you will figure out the weirdness of riding a bakfiets in a few miles. Do pay attention to the steering lock far right and far left to ensure you don't have to adjust where you make u turns. On my Bullitt with a steering dampener installed, left turns are limited, but only very slow and very sharp ones. You install a steering dampener to eliminate death wobble, which given your suspension you may or may not have to contend with. Its rare but not unheard of on Bullitts and my build has it. This is something a more experienced user group will be able to sound off on and either laugh off or advise via direct, specific experience.
I predict you are going to love this bike. A bakfiets is *vastly* superior to midtail and longtail designs under load, and its convenience level is also off the charts by comparison - its a big box you can just toss stuff into without a care for balance or anything else. The Load is unique in that it has full suspension. I have front suspension on my longtail and I absolutely love it. But it has to be done right or the flex will make the bike unstable under load. Something like an R&M designed with it from the factory is highly desirable as a comfortable bike to ride.
I never planned on building three different classes of cargo bike, but I did. What are their strengths and weaknesses?
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I would buy yourself a big/tall canvas duffel bag and use that so you can (cheaply) increase your load capacity. A canvas bag will also limit or eliminate the cargo rattling and bouncing. And start thinking about locking strategies as an 8 ft+ bike needs some special attention. Mine is set up so I carry the lock always in the cargo area and can deploy it in roughly 1 minute. Beyond that I would consider some sort of larger hardsided box. Once you start hauling groceries and such, you start supersizing your jobs and it won't be long before you are hitting Costco and then trying tofigure out how to fit a whole shopping cart in the bike.
Lastly, I would start asking R&M riders what rack fits on this bike (or you say you have bike experience so you can check for frame bosses etc. easily yourself). Thats part of the whole supersizing thing. I load up my front end with the milk jugs and the soup cans. The panniers get the chips and the bread loaves.