But the scoops aren't made of solid material. The scoops is a giant magnetic field that is 100,000 km in radius. The superconducting coils that generate that field aren't necessarily that big! Magnetic fields weigh nothing, they are just lines of force. You just need a superconductor that can carry a large amount of electric current through a loop. The lines of magnetic force are perpendicular to the direction of the electric current. The hydrogen is ionized by forward facing lasers. Since their is not much hydrogen in space, it doesn't take that much energy to ionize them, this energy is increased dur to doppler shifting of the ship's forward motion. The hydrogen has to be slowed down in relation to the ship and collected. Some of the hydrogen has to be fused to continue to push against the interstellar medium while the rest is collected and stored for use by the jump drive. This is not a standard use of an interstellar ramjet, it provides little net thrust and drag puts an upper limit on its velocity, but for the purposes of collecting hydrogen for a jump drive, an interstellar ram jet works fine.To suck in enough material for an interstellar ramjet, the scoops have to be on the order of 100,000 kilometers in radius. Very large.
It'll probably go no faster than 30% of the speed of light as the drag will then be greater that the thrust that can be produced by fusion.