So is it that you have 400 mg of Clomid?
In that case I would look at it this way:
Planned period of use: 4 weeks (another figure could be used)
Total dosage if Nolvadex alone: about 680 mg
Total dosage if Clomid alone: about 1700 mg
So roughly speaking the amount of Clomid needed is 1/4 of what would be used if using only Clomid. Nolvadex can then be dosed at 3/4 what it usually would be.
I would take 20 mg Nolvadex four times on day 1, and also take Clomid 50 mg once, and 25 mg once for a total of 75 mg Clomid on Day 1.
Thereafter I would take 15 mg Nolvadex per day, and 25 mg Clomid every other day.
Other methods could be followed of course but that is what I would do.