It would make more sense to provide a scale drawing of your current sail plan.
You should aim to geometrically match the proposed junk rig to the original Bermudan sail plan (that is, the geometric centres or CEs of the two sail plans should match), if you want approximately the same helm characteristics from a cambered panel junk sail.

I don’t know whether or not this drawing is true to scale, or whether it represents your version of the Sabre 27, but at face value and doing some rough calculations: to match that sailplan a SJR (33% balance) should have its mast at least 30" - 33” forward of the above mast position.
Having said that, I don’t necessarily trust the Sailboatdata drawing, having seen an example which was considerably in error. If your drawing would show the current mast position, and the planform of your current rig, the calculation for mast position of any junk rig is fairly simple.
(The hands-on experience of Frank is valuable in this regard too, taking into account the bilge keels, his flat-cut sail and the tendency of the boat to acquire weather helm when heeling).
I don't include myself in the expert category at all, and I don't have the means for accurate drawing, but my guess is 22" is likely to be marginal to say the least, even for SJR, if the above drawing can be believed.
Maybe you could consider what is a fairly commonplace conversion: take the mast down through the forward hatch, offset a little, and lose one of the forward berths. That would open up a range of JR options. There are plenty of documented examples of thru-hatch arrangements, for example Jes's Mwera conversion (JRA Magazine #100 March 2026).