did a quick search of pics. Most have the uppers right next to the mantle hood. A few had space like yours. Both looked okay to me. It seems if you have them leave the space that the other side should at least be the same distance away as the one in your picture. Not an expert on mantle hoods, though.

A filler as wide as the space between where the side of the hood is and where the lone cabinet is would be way too wide IMO. Does the mantel molding go all the way down the sides of the hood or just across the front? We have a similar hood and our mantel molding just goes across the front which allows the side cabinet to be set right up against the hood. If yours goes all the way down the sides as well as across the front, that is why they are separate. I don't think what you have there looks bad, I think it may just not have been what you were expecting. What do your preliminary elevation drawings that you signed off on look like?

Why is there such a big space when you could probably (based upon the answers to the questions above) used a wider cabinet abutting the hood?

Beautiful cabinets, BTW.
But IMHO, it looks unfinished & kinda stupid.

It looks very deliberate - like hood was designed to be free floating. Once the crown goes in and the uppers for the other side it will look a lot less jarring. What was in the rendering you signed off on? Now is the time to change it if you don't like it, what you describe would be fine as well but it doesn't appear that this is how your kitchen was designed. I'd voice my concerns to the cabinetmaker now but I do think it will look very different when completed. Your decision is whether to stop it now or see the finished install. Either way if you change the design your in for some not insignificant extra charges.

some do it that way. there should be equal spacing on the left side before cabs are put up there to balance it out.

To me it looks as if the hood isn't centered above the space for the range. It looks like it should be more to the right.

you could be right new.bee! I hadn't noticed that. unless it's just the camera angle - but something to be checked out asap.

Sorry, to me it looks odd, perhaps a mistake. I too want to know what you signed off on the original rendering.

The mantle doesn't look centered over the stovetop, but is the stovetop in its final position? Also, when the side cabinet is that narrow, I want to know - what will you store there? is there a reason why it isn't connected to the mantle? why is it a staggered height from the mantle? Staggered heights are pretty if the proportions are correct. But when the cabinet is so narrow, the staggered height looks like someone found an extra cabinet somewhere, with no connection to the kitchen. Also, what about the crown molding? I am not sure how a narrow crown molding for the cabinet will look.

I am so sorry if I sound harsh, but this is your kitchen that you should love, so better to make a correction now. I don't think it will be hard to replace with another cabinet that is wider that would adjoin the mantle (same on the other side). Filler makes no sense, because the amount of space for the filler is too wide, and also because you would be losing valuable cabinet storage space that could be found with a wider cabinet.

Everything looks a little off right now. I agree the range hood looks off from that shot. It might be an illusion.

The staggered cabinets will probably look fine when the other side is in place. Although it appears that end cabinet could have been larger, no matter whether it was to be attached or not.

The ceiling lights are definitely off for the cabinet placement.

Looks like it's made to go over a toilet.

It might look fabulous once it's all put in, though. Surely you have a drawing? If you can post it we might have a better idea what the goal is, and what fillers, etc. are to be used. Might be good!

Does the mantle shelf wrap all the way around? If so, the I doubt that anything else is supposed to go there.

Can you post a pic of your cabinet elevations? The photo that you have posted indicates that the range hood and the cupboard are completely out of proportion. WHat will be on the otherside of the range hood? When all is finished it might be better to just not have that skinny cupboard located there.

Do you have enough cabinet space to just forgo the little cabinet on the side? What is expected to go on the other side?

The problem you are going to run into is that the crown molding is going to likely need at least a 3 inch filler to go back into, so I'm not sure there's a great solution for the sides besides fillers. How high is the crown molding? Perhaps there's a really short pullout of some sort you could put under it and then use dead filler from the crown up?

I'm guessing the space was the cabinet maker's preference over filler.

Did a quick search on Houzz for mantel hood and did not find any with a space like yours.

Looks like it's made to go over a toilet.

ROFL. I have some in-laws who could really do with 1200 CFMs.

This is how I like to do them but it really does come down to the rendering you signed off on.