Hoddo0

Hi, I had a 5 holes pattern, quite unusual (FG538 year 1994) I finally gave up and I am running SRW, no problem.
As far as I remember:
I measured the distance between the external side of front tires, I called F1
I measured the distance between the external side of rear tires, I called R1
I then use D= (R1-F1)/4
If you remove D to the existing offset of your existing wheels,
- the new F2 front wheels distance becomes F2= F1 + D (left wheel) + D (right wheel)
- the new R2 rear wheels distance becomes R2=R1 - D - D
keep in mind, the external rear tire moves inside when offset goes down (conversely does front tire)

so you have caught up the difference in tracks.
Best, use a paper and pen with grid paper to cross check (wheel offset distance= axis of tire minus the rim plate. If no offset at all, the mounting rim plate is aligned to the tire middle line)

Hope this helps. Let me know.
Best,
Bob