I've been watching a few build videos recently, and it's become clear there is a significant amount of dimpling for flush rivets even in the quickbuild kit.

A hand dimpler can be used for for small pieces, but a C-arm clamp is needed for larger pieces and skins. This has a dimple die mounted, which is then hammered down to create the dimple.

There is another tool for this which uses a hinged lever arm to depress the dimple, called a Deep Reach Dimple Tool (DRDT-2) made by Experimental Aero. This has a heavy duty welded tube steel C arm and a press-like arrangement at the front. This uses mechanical advantage, gives more consistent results, and (probably most importantly) is much quieter than hammering the die down.

DRDT-2

The C-arm is very heavy (44lb overall) so the manufacturer kindly sells the press arm (front kit) only and provides a schematic to allow for this to be fabricated locally, so I've approached a couple of local steelformers for quotes.

Still likely to be an expensive tool, but some kind of C-arm will be required to dimple the empennage skins at least, and I'll take any help I can get from my tools.