Nice little write-up, Brian.
Hope you're keeping well.

Currently own two 99s. One bought used from a forum member last year. Totally standard, still very accurate and much less lively than you'd expect for a full-power lightweight springer.
Stripped, de-burred, polished, fitted WonkyDonky spring, guide, top hat and piston sleeve and it's utterly lovely.

Got a new .177 the other day....lovely, too. Some resonance through the forend, but it's still early days, only had 8-10 shots through it as I was running out of time. Will fettle soon and plan to use it for some HFT work. But it's still very mild-mannered to shoot.

Everything I've seen re the SFS Imps has been good. That's a lovely rifle you have there....enjoy!