Getting really clear, bubble-free joints in thick acrylic is not easy. I've done quite a lot of practicing with various methods and eventually did some testing on the materials and cements that I was using. The link below shows the results. Since McMaster plastic is a lot less expensive than TAP plastic, I tend to use McMaster to supply the plastic and I use TAP green label cement on it. I've never tried IPS #3, since I've been told it's identical to TAP green label. I'm not convinced about this and may have to try it some day.