5C3S 5Ц3С Black anode (5U3C, 5U4G) Svetlana St-70 Compatible?

I have been looking for a cheap rectifier tube for my st-70 I am rebuilding.
It is all stock. I have bought the vta boards and will be replacing them and the quad cap.
Wondering if the
5C3S 5Ц3С Black anode (5U3C, 5U4G) Svetlana
rectifier is safe to use in the st-70 with cloth wiring pwr transformer?

As they are cheaper then new 5AR4 from my searches.

I did try one in my original Dynaco and in my VTA. Both do have the bigger power transformer. The 5C3S did work but it did cause me some concerns. My VTA 70 has a time delay start module to allow the tubes to warm before applying power. With the 5C3C when the power was applied there was a blueish glow at the top of the tube, not exactly a flash, but like a halo effect for a brief second. Only happened when they relay clicked in. I didn't like that and no other rectifiers I've used has done that either. 

It also looks to me like the tube would draw more power too, which may add more load to your transformer. It also lowered my B+ voltage from 388 volts with a GE GZ34 to 353 volts with the 5C3C. I wasn't able to hear any difference in sound though. 

I  do like the look of the tube though. I just don't trust it. I will also add that I am no expert. I'm sure someone else can answer your question better. Just my experience with it. I will try to add a picture of the paper included with the tube as it might help you.

Thanks yes it looks like it pulls more current. I am hoping with a thermistor installed maybe it will be fine.