Well tbh I would say the best and easiest way to break atypical dominance is just topping,not only does it slow growth to immediate surrounding nodes but allows these side branches to catch up to tallest parts of plant, that itself prevents a dominant cola from forming and distributes that growth to the lower parts of plant,removing as much red light as possible helps break this as well blue light boosts leafy veg growth or horizontal growth. I know you said you don't want to top this run, so the only other way to achieve this aside from selecting genetics that do this naturally,is to tie your plant down horizontally in pot and allow the side branching to form the new canopy. This breaks that main cola effect,let's u deepen your canopy and keep plant tight to save space. It's a ok method but it's really not as effective as strategic topping ....
