Printer Firmware Modification

I need help analyzing and modifying a printer firmware file in .efu format. The project may also involve related file types such as .bin, .rcf, and .rcx.

The primary goal is to add new features, so experience with firmware modification is crucial.

Ideal skills and experience include:
- Proficiency in working with .efu and related file types
- Strong background in firmware development and modification
- Experience in adding features to existing firmware
- Problem-solving skills to analyze and implement modifications

Please provide your relevant experience in your application.