I have a 2014 Look 695 Aerolight with a ISP...the problem I have is that the post topper (E-Post Ti) has a 30mm offset. I generally have a 0 offset on my 54mm/55mm bikes as I'm short, 5'9" with a short inseam. I've managed for years by having the topper adjustment pushed as far forward as possible, but unfortunately, the fore and aft mechanism is then unstable and will slip backwards.
I see no solution to this issue with the current topper and does Look makes a couple of additional toppers, the R5 and the R32 which have a 0 degree offset or are reversible, but needless to say, they impossible to find.
I've read some comments over the years about converting the ISP to a standard seat post or possibly utilizing another brand topper, so I was wondering if those with longer experience might have some guidance.

I own a Look 595 that also uses that same version of the Epost. In my case, the ideal adjustment is in the middle of the setback range. I did at first have problems with the saddle slipping back in its clamp, but I eventually sorted that out. One great feature of the Epost is the mini suspension that it provides, it really takes the edge off when riding rough roads. The Epost is proprietary and incompatible with any other integrated seat mast design. In any case, any other setup with an integrated seat post requires that the seat mast be cut off much higher, so even if you could find one that would fit your frame, you would be eating your knees while pedalling. I have no idea how you could convert your frame to be able to use a conventional seat post. I suspect that you would have to fabricate some sort of seat clamp that would fit inside your seat mast. The downside would be losing that micro suspension incorporated in the Epost. Lest you think that isn't important, my bike came with the first version of that setup that didn't have that elastomer suspension and believe me it makes a great deal of difference. Maybe try to figure out why your seat clamp moves back. If you can cure that problem you will have the best solution unless you can score one of the versions that have less setback