I have changed the LCD design for this project. The dose now displayed with bigger font and the CPM value with smaller numbers. Dose now has only 3 digit with float point and it displayed by auto in uSv/h or mSv/h (depend on the value). Maximum value that can be displayed is 9.99 mSv/h; minimum value is 0.01 uSv/h.
Sound on/off and battery indicator was added. I also made a lot of work with internal code optimization. High voltage is supported by auto to 400V app. and it independ from battery voltage changes, so it stay stable even if batteries will go down to 4V.
I thinking if it will be right or not, to use Li-poly battery with 5V step-up IC and charge circuit. Personally I like this option, but it will require SMD components to be installed on the PCB. I still thinking about this. It can reduce weight of the final product when installed to the box. Anyway 4.8V Ni-MH battery will do the job perfect.