will actually depend on the angle of the diamond?
Generally speaking, a double or single slip would be as per, for example, the Peco item.
If the angle between the crossing tracks is such that the 'radius' of curve between one track of the diamond, and the other track is going to be excessively tight, ie outside that found on ordinary turnouts, then the pointwork would likely consist of several turnouts (2 or 4) positioned closely together (ie overlapping) with a diamond in the central position.....ie tailor-made to suit the site.
for our purposes as modellers.....and indeed on the prototype, a single or double slip is a space saver..therefore I suggest going as per the Peco items.......what I assume you mean by an ''inside'' slip?
If tailor-making your track layout.....as described above...try and avoid having the actual diamond on a curve.
Either way, for pointwork as you describe, both can be found somewhere.....
