If any of the system is original, or used NOS parts, you cannot use dot 5 silicone fluid as it is incompatible with natural rubber seals. If you have a new system, it must be complete cleaned with alcohol before switching to Dot 5 as Dot 4 and Dot 5 have different swelling properties and cannot be mixed.. if you don’t you will soon see black fluid in your reservoir… the black is the seal particles that have left their “hosts”.
additionally, Dot 5 is compressible, while Dot 4 is not. you will always have a slightly “spongy” pedal when using dot 5 fluid.
I understand the attraction of dot 5 as it cannot absorb water. like dot 4. Periodic maintenance was once an accepted fact of owning a car… people have gotten lazy. Brake fluid should be flushed and changed at least every 2 years.