It is a great learning experience and I wish I had started my spey journey with scandi because it forces me to use my bottom hand.
I've had so many years of casting using poor technique and overuse of my top hand that its very easy to automatically default into top hand mode.
I know just how you feel!
After over 20 years of long heads (DT lines originally then Rio
Accelerator / Grand Spey & other long Spey heads) & big rods (15' 6" & 16 footers generally); &, whilst not wishing to brag, I got pretty good at it. Then I decided to transition to Scandi heads -which I think is probably down to a masochistic streak seeking further challenges!
So my casting went down the plug hole for a while as I used too much top hand, too long a casting stroke, too much power - you name it & I did it!
But (& I admit because of my instinctive learned muscle memory it probably took me longer than if I'd been a newbie) eventually I started to learn to shorten everything up, keep it all very compact, & "flick" the rod rather than "driving" it forward & it is finally coming together.
I can still cast further with a big rod / long line combo (there's a reason they use these in competitions), but I can cast all day with less toll on my body with the Scandi set up. I'm going to be 57 shortly & have more than half of those years worth of wear & tear with big rods & lines on my shoulder joints & muscles. I don't intend giving up any time soon (at least not voluntarily) & thought that the swap would allow me to keep fishing for longer without problems; I hope that in 10 years time when I'm retired I'll fish more than I'm able to now.
So I still dig the big guns out now & again when needed but most of my time I fish Scandi heads & I'm still on the learning curve compared to what I'm used too - but isn't the acquisition of knowledge what got us out of the caves to start with?
So stick with it, it will come together - honest!