Build Your Own SLA/SLS

Although stated as not needed, has anyone still done this and got better results?

Yes the following modifications help particularly at higher resolutions:

Lowering the lens about ~2mm helps center the lens for printing and reduces blurring at the top of the image
Stepping out the lens ~5mm helps reduce spherical aberration issues across the build platform
Zooming down as much as possible also helps. Removing the zoom stops gives more range.

In practice this improves focus over most of the build platform (for Acer 6150) but I still avoid using the corners due to: lower intensity and increased incident angle worsens bleed. see http://robotsinthesun.org/dlp-printer-b ... tribution/

Is there any guide on how to modify the Acer P1500? The edges on some of my prints are not coming out. This is a recent development for me. I have had pretty great success until now. I can't afford to buy a whole new projector.

Note there is a useful a lens modification guide for the Acer X1240 at http://imgur.com/a/FOgXW The Acer 6150 and presumably the 1500 are very similar. The specific steps for the 6150 lens modifications include:

Once the lens is off and the zoom adjustment screws out. Pull the zoom adjustment ring off.
Remove the 3 zoom stops and push the lens assembly in fully from the rear to zoom down as much as possible. Note it can drift back but this can be fixed with a fine screwdriver after reassembly.

To enable recentering of the lens, dremel the black plastic mounting screw holes in the lens assembly so the lens can sit about 2.5mm lower.
It is worth masking off the rest of the lens to protect against dirt.
Add spacer nuts and washers to offset the lens by 5.3mm and enable focus at 28um xy. Probably less than this is needed for 35-50um xy resolution.
Reconnect the lens assembly and slide it down to close to level with the bottom of the plastic projector housing. I've found you also need to move it slightly away from the fan. Tighten and test the projector to see if the lens focus is centered ok vertically and right left. This may take a couple of iterations.
The projector will then need to be realigned with the build plate. This will probably involve more spacers to elevate it.
Refocus.