I don't think this will work as you expect. Adding allowances is like telling your payroll department to withhold based on a lower income because you intend to use deductions on your 1080. When you contribute to your 401(k) pretax, payroll already takes that into account. When your company runs payroll they deduct pretax contributions and allowances from your federal taxable income for the purposes of cutting your check, but you'll still owe the taxes on the withholding reduction you create through allowances. Basically you're shifting when you pay from payday to tax day.
Philociraptor beat me to it. At least in my case, my payroll takes the 401k contributions into account.
In other words, all other things being equal, I will not achieve a higher tax return by increasing my 401k contribution. I will pay less tax, of course, but this is already accounted for by reduced witholdings associated with my 401k election.
I think OPs plan will result in a very unpleasant surprise come tax time