Have you thought about buying a double oven rather than 2 single ovens?
We have a westinghouse double oven and it takes less space than 2 separate ovens because there is only one control panel which houses the controls for both ovens.
Even though you and your wife are very tall, I would be concerned about having the bottom of the top oven at at 170cm, meaning the top of the oven would be around 230cm. Seems to be a safety issue. And for resale you would limit the interested buyers.
It could be awkward to bend down to the oven beneath the bench, given your height. Plus if you have young children, an underbench oven is a safety risk.
If you post the space you have to work with, I'm sure you'll get some good ideas from others.

Hi Liz,
Thanks for your comments.
Attached are the perspectives, it is a bit of a stretch I think.
But really wanted to try and maximise the ability for more storage for ‘daily’ appliances like the toaster, whilst also putting two ovens in that section of the kitchen and not sacrificing other cabinet storage.

I think we could find a child safety lock for the door, perhaps

Plan view

I see you have a 2nd post on the same issue with lots of comments, ATo.

Do you need actually two ovens?
We only have two because it was to replace an old oven/microwave stack and a double oven was all that could fit.
We don't use the bottom oven since having young children in the house. A lock solves one issue, but doesn't deal with the risk of burns.

Your kitchen space is bigger than mine, so don't think it is small, but the door to outside limits layout options.

I had been playing around whether could change my U shape kitchen to have direct access to the outside eating area, but have found that it compromises what I can fit in.

Perhaps have a rethink about the entire layout and what storage you need rather than go ahead with plans which don't really work.

My first time posting and I wasn’t sure if it worked, so ended up with two threads! 😂

I don’t really think we need two, but the wife is adamant. I think we could get away with a big combi steam oven, but we sometimes steam and roast at the same time when we’re entertaining ..

Yes this darn door outside!! I never thought of it as a negative, but Houzz is certainly educating me, albeit I don’t think i can implement all the knowledge!