With your level of experience, Daveo, and the equipment at your disposal, there's a very good chance that you could achieve the same, or similar, results from a tune as some professional tunes.

I'm not exactly sure to what extent the SFS guns are tuned, but I have tried one or two and they shot very nicely.

Now, back in the heyday of spring gun shooting, Venom (and very possibly Airmasters) would divert plenty of attention to ensuring that the cylinder was straight and true and then check the concentricity of the piston rod. All this on even a "standard" tune. The full on conversions, like the Lazaglide, took this up to another level and were re-engineered. V-Mach will do the same nowadays.

I believe, also, that a responsible professional tune will then devote much time (Steve Pope refers to it as "bench time") testing power and consistency with a range of pellets. They will have the fine art of individual piston seal sizing down to a fine art and will have a range of springs at their disposal to undertake this fine tuning.

Although, like your self, I've fettled a fair few springers, my Venoms and V-Machs remain intact as they left the Pope Dynasty, as I actually like that little air of mystery and it just seems right to me to leave them alone, enjoy them and revel in their lovely shooting manners.

The single biggest factors in making a springer feel more refined are de-burring and removing any twang. After this, many may well struggle to tell the difference in various internal set-ups and personal preference also plays a part. Some like a softer cycle, others quick and snappy. The acid test really has to be accuracy and the ease in accessing that accuracy to suit the required use. So, for a HFT rifle, hold sensitivty will be a far bigger issue than for a rifle that's always shot from a bench in the same position.

Hope this helps a little and I love all my springers - Venom and V-Mach tuned, one of them a Lazaglide, some with V-Mach kits fitted by myself and some with Mr Bum's guides.