i dont know that TSK extreme gene unfortunately.
but if the snake really is what he says it is, then it means that these two variants of hypo must be compatible. its a visual hypo after all.
so yes, why not breed it to a butterscotch hypo. i guess you would get a clutch of all hypos, you should get 50% butterscotch and 50% of that TSK extreme + butterscotch combo.
That is, if my assumptions are correct and this is analogous to breeding a lesser mystic to a super lesser.