Extreme programming (XP) is one of the widely used software process model for the development of small scale projects from agile family. XP is widely accepted by software industry due to various features it provides such as: handling frequent changing requirements, customer satisfaction, rapid feedback, iterative structure, team collaboration, and small releases. On the other hand, XP also holds some drawbacks, including: less documentation, less focus on design, and poor architecture. Due to all of these limitations, XP is only suitable for small scale projects and doesn't work well for medium and large scale projects. To resolve this issue many researchers have proposed its customized versions, particularly for medium and large scale projects. The real issue arises when XP is selected for the development of small scale and low risk project but gradually due to requirement change, the scope of the project changes from small scale to medium or large scale project. At that stage its structure and practices which works well for small project cannot handle the extended scope. To resolve this issue, this paper contributes by proposing a scaled version of XP process model called SXP. The proposed model can effectively handle such situation and can be used for small as well as for medium and large scale project with same efficiency. Furthermore, this paper also evaluates the proposed model empirically in order to reflect its effectiveness and efficiency. A small scale client oriented project is developed by using proposed SXP and empirical results are collected. For an effective evaluation, the collected results are compared with a published case study of XP process model. It is reflected by detailed empirical analysis that the proposed SXP performed well as compared to traditional XP.