If you absolutely have to cut it to be able to run it through the frame connector, use a solid bulkhead fitting flared on either end, not a flex hose. Flexible hose should be kept to a minimum to preserve equal pressure throughout the line.
The brake line generally has to cross under the frame somewhere, the OE line goes under the rear frame kickup.
Some might argue that cutting the front to rear lines is common when you splice in a proportioning valve but the valve is rigid and usually mounted solidly to the frame. Flex hose is not a good idea except for where it has to be used like between the caliper and frame or at the rear.
