Ken has often demonstrated sliders, and that is what a "portamento slope" is. They are also referred to as "sirens" because that's what they sound like. Continuous low to high, and back down, OR high to low and back up. They can be one octave, two octaves, or just short interval sliders. You could even do a slider that goes from your very lowest note all the way up to the highest note you can sing and then all the way back down.
Ah I didn't know that was the same as sliders. Ken said last year he had a exercise that would help me with my problem, perhaps that's what he meant
This is a classic" example of what I have been saying about SLS. (where bringing the head voice down into the mid and upper mid voice chest registers "favoring or pampering" the chest mid voice which over time causes it to atrophy and weaken (or in many cases disappear altogether and then the voice automatically "flips" into head voice uncontrollably).
All is not lost.
I hear a defnite lack of support in your workout. Focus on this first. (hard)
Then, instead of a scale, use a portamento slope to get to the notes staying with the same key as the current scales. Monitor "what it's going to take" to maintain open throat but push a little (not a lot...a little) to keep the voice from flipping. You will notice that little by little your upper mid voice will start to come back a note at a time.
I deal with this a LOT also in another context with sopranos. Often in classical music, there is so much emphasis placed on the "money note" that conductors are willing to compromise the integrity of the soprano's lower register, encouraging them to predominantly stay in head voice. The same problem occurs. Their belting chest register atrophies and and becomes very weak so they too "flip" into head because of this.
I have an exercise tha REALLY helps with this but is not one I can explain here. I will try to remember to demonstrate it in my next webinar. Be watching out for this.