Something I hadn't seen mentioned in any connection relative to piston launchers, that I discovered immediately after the first flight of the Blue Star, is that a piston launcher collects more fouling than even the bore of a muzzle-loader! After a single launch, on a 1/2A motor, my piston had so much carbon and grit that it would hardly move, much less slide smoothly the way a launcher needs to. I'm now considering building a tower for routine launching of this model, and reserving the piston (after cleaning) for occasions when maximum performance is an issue.
The launch tower was completed in time for the May 25 launch in Millican, Oregon; it worked very well indeed, and I don't expect ever to mess with a piston again unless I start flying A or larger impulse Altitude competition -- an unlikely event.
This tower is very simple; I cut off a soda can to a depth of about 2 inches, punched a hole in the center of the bottom and glued in a length of 1/8" rod (for compatibility with standard pads); I then taped three 1/4" aluminum tubes to a length of BT-20 (with a couple wraps of tape on it as a clearance shim), stood these upright in the can, tack-glued them with CA, and poured about two fluid ounces of 12-minute epoxy around them. The can reached an external temperature of about 120 degrees F during the cure, the epoxy cured hard and slick in the can even though the portion in the mixing cup remained tacky.
After the above steps, I found I couldn't get the tower adjusted to hold the model securely without binding -- until I cut the tubes off to a length of about 20" (as opposed to the original full 3-foot lengths I used). Once I did that, I was able to get the tension adjusted, and it works great! I put a length of masking tape between two tubes an inch or so above the top of the can to support the rocket, and a layer over the edge of the can where the igniter might touch, to prevent shorting, and every launch so far has gone smoothly -- no binding, no tip-offs, and the rocket goes about as high on a 1/2A6-2 from the tower as it did from the piston (though I suspect a larger motor might still gain more from the piston).
After several good flights from the tower, at one of the Monroe launches I apparently had a misadjustment in the tubes that form the launching channel -- the rocket seemed to tip while still in the guides, and took off at a sharp angle, about 45 degrees off vertical, on a B4-6 motor. This trajectory took it over a bird refuge next to the flying field in Monroe, where the grass and weeds have been allowed to grow unrestrained, before ejection. When a model less than a foot long, with a small streamer, goes down in grass six to seven feet tall, it's lost -- though I had to walk the line along which the rocket fell to convince myself of that; it was more work pushing through that grass than pushing a light car, and I could have walked directly over the model without seeing it.