From the Aircraft Spruce website, the drag spec on a rod and ball transponder antenna is listed as 0.41 lbs. at 250 kts. The blade type lists as 0.09 lbs. at 250 knots. Drag increases by the square of the speed, so at half the speed (125 knots), the drag is around 1/4 the numbers listed. If you are concerned about the .0225 lbs. in extra drag vs. the .01025 lbs., buy the blade type and keep the yaw string straight. You will probably increase your final glide numbers by at least a couple of yards.