If I may give my opinion to that subject: Itīs very personal, but nevertheless. I put all my models next to each other and astonishingly, I mostly have 1/24 kits. So my Pocher Porsche 911 in scale 1/8 was very outstanding and kind of killed the nice look of all the models together. I know itīs just a visual opinion, but ... So my advice, I youīre into one scale, donīt mix it up with different ones.
If you think thatīs freaky, just ignore, what I wrote.
Adding to this I need to admit that Iīd love to build the 1/12 Ferrari 641/2 even though I will need to put into a different shelf according to what I just wrote.