I put a set of used Elka Shocks on my wifes 2018 F3L a couple of years back. She already had the BajaRon sway bar and she said that the sway bar was a night and day better difference in the handling. Then when I added the front and rear Elka shocks, she said it was a completely different ride, especially in the twisties and the better handling on the bike.
A couple of months ago I traded in my Indian for a 2019 F3L. It already had a BajaRon sway bar, so I cannot speak to the difference over stock but my wife did have a set of Front Elka shocks put on my bike at Lamonts Spyders in the Ozarks. They were installed by John from Elka in Canada. John told me "NOT" to buy the rear Elka shock since I only rode 1 up. He said the rear makes ZERO difference in handling on my bike. He talked about how it would make a huge difference in ride if I was two up on my bike over the stock shock but that since I was riding 1 up that I would never notice a difference and not to waste my money on the rear. He did say that if my stock rear shock ever went out that I should then consider getting the ELKA rear shock as the price of a new OEM shock over an Elka was not that much of a difference.
I will tell you that in my limited time in riding a Spyder with only the stock OEM shocks and then riding with Elka front shocks was quite a HUGE difference. I noticed it immediately in turns and how the bike just handled better in the imperfections of the road. I would 100 percent get the Elka front shocks again if I had to make the choice from scratch.

BTW if you have any questions give Elka a call and ask to talk to John, he had a ton of information about shocks and ride.

Hope that helps
John