I'm not a fan of kickstands for my own use. I can nearly always find a wall, fence or tree to lean the bike on, if not I lay the bike on it's side, drivetrain upwards.
But the users of the pool of 6 bikes I maintain for a nature reserve insist on having them.
The two second-hand electric bikes have substantial kickstands that attach to custom mounts on the chainstay near the rear axle. They work well, but are not an option for retrofit to a Thorn.
Two of the non-electric bikes I renovated had relatively lightweight frames without plates to mount a kickstand under the bottom bracket. I used Hebie 672V Fox kickstands that are bolted to both the chainstay and the seatstay :
https://www.bike-components.de/en/Hebie/672V-FOX-L-rear-kickstand-p56518/?o=1000180855-black-29-It is possible to get the parts needed to fit an under bottom bracket kickstand to a frame which doesn't have the appropriate mounting plate brazed to the chainstays. But as the single bolt has to be really well tightened, in my experience with second-hand bikes, the chainstays often get deformed or slightly crushed.
The other two renovated bikes had plates brazed between the chainstays to accept a bolt-on kickstand under the bottom bracket. On one of these I fitted a Hebie Central Kickstand 630 LEX :
https://www.bike-components.de/en/Hebie/Central-Kickstand-630-LEX-p20531/This is cheaper than the 672V Fox, but the single bolt needs to be done up REALLY tight.
The other one (an old Peugeot) still had the original Heslin kickstand.
Bear in mind that I am not a fan of kickstands, but on test rides with these 6 bikes I preferred the stands that fit near the rear axle, they seemed more stable with heavily loaded rear panniers (think shopping or cycle-camping). Of the two under bottom bracket stands I reckoned that the Hebie Central Kickstand 630 LEX was better than the old Heslin, probably because it was adjustable.
The two Hebie kickstands come in several versions, designed for different wheel sizes. But there is some adjustment.
All the kickstands I mention are compatible with a Duramaxx Mountee trailer that has the towing attachment bolted to the rear axle.
