Power required goes as roughly the cube of the speed. Going from 22 to 25 knots, say, is
fantastically easier than going from 30 to 33 knots, even though it's only a three-knot change in both cases.
I don't know the exact internal arrangement of Lion, but you're not going to add more than two compartments of extra machinery.
Let's say you go from eight to ten compartments (10-19, rather than 10-13, 16-19), and let's say your new machinery is 25% more powerful per unit volume. By our naive rule of thumb, this 50% increase in power should get us a 50% improvement in the cube of the speed ratio. That would take you from 28 knots to about 32.
Of course, there are limits to how much power you can pour in, and you're not optimized for those speeds or powers. I think you'd be very, very lucky to achieve meaningfully more than 32 knots. 34 knots is plainly not happening IMHO; Alaska required 150,000 shaft horsepower to reach 33 knots on similar displacement (vs. 70,000shp originally available to Lion).