No problem, I bought the 90mm & 75mm focus cones, and fitted a 75mm f8 SA and a 90mm f6.8 Grandagon. However I found I liked the 75mm so much I've never bothered using the Grandagon. In fact I've taken it off the Gaoersi mount and put it back on my Wista.
I love the wide format with a wide angle lens, and really enjoy using it, there are the odd occasions where I might need to switch to 6x12 but they are quite rare.
My decision to use 6x17 was due to frustration with 5x4 which just wasn't suitable for some of the images I wanted to make, and I needed something wider. Remember that the 75mm is a fairly standard lens for the vertical 6cm dimension, and is only wide for 12cm/17cm.
There are a couple of images on the 3rd or 4th page of my APUG portfolio with the Gaoersi. Here's another:
The 75mm f8 Super Angulons seem to be quite reasonable prices second-hand, I paid about 200 euros for mine, 2 years ago, boxed and it appeared never used, I've seen several for similar prices since.
My Gaoersi is not a light camera but that makes it easier to hold steady. Hope that helps