Fixing Plain Tiles Along Hip - How?

Our bedded 1/3rd round hip tiles have seen the end of their lifetime with all the mortar having crumbled away. We'll be replacing these with a dry fix system.

Upon lifting the existing 1/3rd round hip tiles, none of the plain tiles (cut at angle to align with the hip rafter) are mechanically fixed. They obviously relied on mortar and the weight of the hip tiles to keep them in place. Would this have been the correct way to install them in the first place?

What do we need to do (if anything) to the loose plain tiles along the hips before the dry hip installation? I see three options, are any of these correct?

A. Leave these tiles loose and rely on the adhesion of the dry fix roll to keep them in place, together with the compression of the 1/3rd hip tiles once screwed down?

B. Grind slits in every tile/drill holes and screw into the nearest batten or at an angle into the hip rafter?

C. Gripfill the tiles down?

Do they still have either of their nibs in tact, or are they cut at such an extreme angle there's nothing there?

D) buy some tile-and-a-half matching tiles so that you can still have the angle cut, but that will leave you with enough meat in the top to hang them by the nibs.

All have had nibs cut off. Furthermore, replacing most with tile and a half's will still mean nibs need to be cut off...

Slate hooks

If you have a disc cutter you make a horizontal cut where you can pick up a batten to nail them.