Greg,
Years back when I was an active speed flier I used both the mousetrap type and pin type dollies. Both worked for me. The pin type is easier to build but you need a smooth surface to prevent bouncing out. I liked having the vertical pins close to the fuse. The ship should sit flat/level in the dolly no nose up. You need to build either type so you can put the ship in the dolly and hold the ship and dolly around the fuse to start the engine. You need to have access to the needle valve and be able to set it and safely set the whole assemble on the ground for release. Use rounded profile wheels not thin pointy one to allow it to roll over little bumps/ruts without getting railroad tracked. Remember to slowly walk back as the ship starts moving to keep the lines tight and off the ground. Don't hold up elevator coming off the dolly, hold neutral or very slight down (like a stunt ship smooth take-off roll).
Most speed designs are high wing and will have a nose up pitching moment plus the nose up torque reaction so be ready to ease in the down to keep it from getting to high in the hemisphere (we use to hand launch them and you had to hold significant down elevator at launch to get the nose to come over flat, once it got flat back to neutral, see attached pic of John Kukon father hand launching his speed ship in 1962). Basic trick is once the ship gets to the low point of its path pump the down to kick the nose flat, always control at the bottom, up elevator doesn't do much except stall the wing.
Best, DennisT