Those interested in this topic should have attended the Delta Nu Alpha/NTBA seminar on this exact topic (compensation).
http://www.insidetransport.com/delta-nu-alpha/12875-delta-nu-alpha-october-function.html
For the record, I currently work in operations and have zero 'real world' experience negotiating salaries with sales although I did spend several years in sales so I'm trying to see both sides of the coin...
Not picking on members, just being devils advocate:
The suggestion of a higher commission base early on with a sliding scale (lower) as the volume of business increases sounds great. What if all the early business is hardly any marign (not a win for the company)? What if the business brought on much later on is huge margin (not a win for sales as it's now paid on a smaller percentage)?
Looking at a compensation strictly from a revenue perspective is great, however; what if 'every' single order for the Fortune 500 company requires you to dedicate a large amount of resources (sales, dispatchers, customer service, admin, etc...) and ends up costing you more in resources than it brings in profits, but Jimmy's Machine Shop is a 1 phone call order and high margin?
What makes the most sense is a win/win situation, there are many ways to view this and all factors should be considered (including costs).
I wish I had the magic percentage for you, the bottom line is that both employer and employee need to have the same goal (is it low margin, high volume growth, high margin low volume steady paced growth, maintain current revenue but elimintate customers that cost more than generate?)... Once they can agree on what the 'goals' are they should be able to come up with the right copensation to achieve and reward accomplishing those goals whether it be revenue, profits, new customers, etc...
Pardon my ramble, I realized half way through this that it is DARK outside my window and it has slightly distracted me, not even 5:30PM...
Keep well,
Mike