Research by Proposify suggests that when the prospect has already made the decision to buy, a simple proposal is all that is needed. How else do you explain these results?
Complex solutions cannot be communicated in two pages, so It is hard to avoid the view that the chart below is explained by the following reasons:

• The majority of two page proposals are for simple solutions
• Many clients need a confirmatory proposal for governance reasons and so the proposal need not persuade, just quote the fee
• If you can explain your solution in less than ten pages, do it!
• Doubling the scale of your proposal does not double your success rate!
• After 15 pages the scale of your proposal makes little difference to the success rate
• Anything above a 35% win rate is a good result!