Own design is an interesting concept. I did not see this exact thing elsewhere in the exact form I will provide you( or anybody who asks ) with. I have build a few linestages, and will build a few more before I am done. This is about as simple as I think it can be done and still deliver 'the goods'.

If you are going to go DC on the filaments, the Hammond 261C6, E6, and G6 are all capable of running the rectifier, and are a bit cheaper.
regards,
Douglas