I think even P&G has said that you can use HE detergent in a top-loader. Recent market introductions of new formulas seem to have them useable in either deep fill top loaders or HE machines.
If you really are curious about dosing in your particular formula, call P&G and ask them. I suspect they won't even suggest adding extra detergent. Lower or no suds is definitely going to be a result, though many of us like that element, as some have said above.
Let us know how it works out!
Gordon