Add Commercial Proposal to Existing Technical

I need a skilled proposal writer to create a detailed commercial proposal that perfectly complements an existing technical proposal. The commercial proposal should specifically focus on describing the payment terms and conditions. Please ensure that the commercial proposal maintains the tone and style of the existing technical proposal.

Ideal skills and experience for this project include:
- Experience in technical and commercial proposal writing
- Understanding of project management and payment structures
- Detail-oriented, with a knack for structuring information clearly
- Ability to adapt to an existing style and tone

The commercial proposal should be a detailed breakdown of all costs and payment schedules. It should not only outline the payment terms and conditions but also have provisions for addressing any changes in scope or unexpected costs. These changes should come with a fixed rate.

If you have a background in both technical and business writing, that would be a plus. Please provide examples of previous commercial proposals you have developed, and indicate how you would approach this project.