On road or track
(and it sounds like you are talking about track work cuz on the road there is no need to keep it pinned and shift like that for a better time..) so I'll base my answer around track riding..
There are corners on tracks in the uk that require 1st gear, Shaws hairpin at Mallory for example. There you (or at least I) will be shifting from 4th down to 1st. On my gsxr600, I will go down a gear at a time, blipping the throttle and letting the clutch out each time. This also helps with braking as it give you a more controlled feel and you can use engine braking to your advantage too..
In your scenario, 3rd to 1st, you say you hold 3rd for as long as possible, so maybe doing 12-13-14000 revs?.. Then drop it to 1st and dump the clutch!! IF your tyre was able to grip at that speed it would spin your engine up to probably 18-19000 revs so not only are you putting your gearbox at risk, your engine, valves especially, are being put under immense strain! WELL over the red line of your engine!
The fact your back tyre is bouncing and skipping all over the place should be seen as a warning!
You may FEEL faster like that but I'm willing to bet smoothing out your style would improve your lap times overall!
Most track days offer free instruction. Talk to them, they are a friendly (if sometimes a bit crackers) lot and they will lead/follow you round track and give good help..