Scanning the above posts, some aerodynamic aspects might be worth considering
Stall Speed has a number of presentations to a pilot, namely are we talking the true "stall", or when the first warning signs appear (e.g. buffet)? Are we really trying to lower the stall speed (unlikely), or lower approach speed (more likely). Even the TPs see the need to establish for what purpose you are looking at this, and the various definitions
3.3.2
We can add "devices" to our wings to increase the stall AoA - airliners use slats, but there are the RV-8 "cuffs". I am dubious about these, and suspect what they do is remove the buffet warning of the stall due, as stated above, by the gear/wing intersection. They also pretty directly affect the inboard flow above the wing, which at high AoA goes right over the static port and that creates it's own questions.
In the UK, all RVs need an artifical stall warning system
except the RV-8, where the above buffet is seen as a benefit.
In a nose dragger, delaying the stall to a higher AoA e.g. VGs will just result in landing on the rudder. In the tail dragger variants do you really want to be getting min landing run by landing tailwheel first and then dropping the mains on?
Aileron droop is used on a few types, and as above, once on the RV-3. Bear in mind flap / aileron droop increase effective Incidence of the wing and such stall will occur at a lower AoA. With Flaps (only) this has the benefit that as you do stall it, at least wing drop is minimised since the root will stall first. Aileron droop risks stalling further out, with a dramatic wing drop at just the altitude you do not want it - and bear in mind you could be nicely set up, just off the stall, and it is you that triggers the stall by use of aileron
And given how often we all forget to raise the flaps, think of the issues of Aileron Droop flaps up
Clearly you can reduce the approach speed by just flying closer to the stall - but at increased risk, balanced against field length considerations. As others have said, pilot technique is probably way more important than mods.