Robert, it's difficult to tell from your description whether your enlarger is a condenser type, or a diffusion type. A condenser type enlarger usually has a way to adjust the placement of the condenser lenses for maximum light output for each size format. Condensers allow a less powerful bulb to be used. They can focus the light into a stronger, narrower beam. A diffusion type enlarger uses the inside of the lamphouse as a reflector. It gives off a larger, wider beam of light. It takes a larger more powerful bulb. However, it usually needs heat absorbing diffusion glass between the bulb and the negative to prevent overheating the negative. If you were to use a large hot bulb too close to the negative, you may experience curling and/or cause permanent damage to the negative. There is always a trade off between the size of the bulb and the printing times. the larger bulb placed farther from the negative probably helps to avoid heat build-up, but printing times are going to be slightly longer.