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To really do it right, you need to make current and voltage measurements for each tube or supply, and figure out exactly how much voltage you need to drop to get down to the specified levels for each supply. Find the required resistance and wattage using Ohm's law. For ballpark guesstimates, figure on the output being 30V or so higher using silicon.
5U4s are directly heated tubes, and produce B+ in a second or 2 from a cold start. A bit slower than solid state diodes, but still not "delayed B+" by any means. Certainly not like a 5AR4 or other indirectly heated tube.
Where you might have an issue is the 30 seconds or so between power on and the rest of the tubes starting to draw current. You need to make sure that the output of the silicon diodes doesn't exceed the voltage rating of the filter caps during this time.
I prefer the 1N5408 to the 1N4007. 3A continuous If is probably overkill, but the charging surge can be pretty tough on 1N400x series parts. Mount a pair of them in an old octal tube base.
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