To displace the turnsignals is not an option for me too.
So I first used these bags:
https://m.louis.de/artikel/vanucci-vst07...b8d03c6958
but without C- Bows, a previous version.
When the zippers gave up I changed to old leather saddle bags bought together with a VT1100 and which stays with me also that Honda has passed away. Both kind of bags are connected together with stripes which can be laid under the saddle. Fehling Distance Holders prevent the bike from being damaged by them. There they are fastened with some one way plastic stripes. I prefer leather look over textil and use leather wax to make the leather bags more waterresistant than they naturally are for daily use.
On longer trips I use Ortlieb plastic, spacey and waterproofed ones which also fit this way.
2 things should be kept in mind. You sacrifice some legroom for a sozius if you mount them this way. He should be very flexible...
Also be aware not to partially cover the lock of the saddlebank under it. This is no easy job because their isn't much space for the connecting stripes. Otherwise the bank can't hardly be removed again once locked because the locking mechanism will be hindered to open up again.
Wisedrum