Well I got mine in today from Germany. KIEI has them for sale but even with overseas shipping I still got mine cheaper. Anyway, it slips over the mag just fine, a little loose but not much and when the mag is inserted it feels just like the full size. I haven't shot with it yet but I can't see anywhere were it would be a problem. I have used my compact with full size mags for USPSA shooting and I haven't had any problems. I can only assume the the grip extensions would just help to further safe guard the ejector/extractor when making a quick mag change...
Jkstrr