I have a sf400 version r.I notice that the front suspension is too soft,especially when i use front brakes.So i was look what i can do for that.You know that the version r(PB1 also) don't have preload bolds at the front springs.
New aftermarket springs (WP or HyperPro) it's too expensive here.(about 150-200euros).Original springs is more expensive.So i have found a crashed version s equipped with preload bolds with no damage(like new),and i grap it at 20euros.

The version r extensions(spacer) beetwin spring and bold is 20cm.So i cut it off,to 19cm because the version s preload bolt is bigger by 1cm than version r simple bolt (with 0 preload).Τhe fastener threads are exactly the same.
I have also change the forks oil and the suspension is like new.Now i can preload the front manually,like with rear shocks suspension.

It's a good job :)

I bought Hagon springs for an old XJ600S once. I couldn't believe the change in the bike from just that.

If you really want the front sorted, get newer forks as an assembly. If you want it to be much much better, get new springs. Yours might well be worn out by now anyway. But what you already did is good :)