That isn't with PVC, and the 90degrees thing isn't a hard rule, especially with static tips. I've made a number of bows with a decent amount of reflex, some with static tips, and some with working tips, including some of very similar design to what you are doing. I've made force-draw curves for all of them. As a result, I've built up a pretty good understanding of what the curve is going to look like based on the bow design for pvc bows. For example, this bow: https://plus.google.com/103669557145071686523/posts/boddxXrc5gB
It's got 44" of pvc and an additional 6" on each limb to the string nocks due to the siyahs. It's starting to stack some by 27", which is fine because my wife has a short draw.
You don't have as aggressive of string bridges, (compare the kink in your string at the bridge at brace height to mine) so your initial hump will likely not be as large, as I don't get string lift-off until 18 inches.
You can see a some pictures of the drawn bow here: https://plus.google.com/103669557145071686523/posts/9bJf8bzNerP
She's got it pulled to around 25 inches there and though the angle between the siyah and the string is nowhere near 90 degrees, the angle between the string and line drawn from the knock to a tangent point on the limb is getting close to it, which is why I would expect it to start stacking soon.
With your limbs being a bit short I expect it to start stacking a bit earlier, probably at about 25". I may well be wrong, which is why I'm curious about it. I would be very surprised if this draws to 30" without a noticeable increase in added force per inch of draw length occurring. If that doesn't occur, I'll be copying your design with another inch or two knocked of the length and have an awesome new compact bow to shoot. Awesome look and that sort of energy storage would be tough to better.