I've used the C10 for about ten years and I agree that it can be a rather powerful instrument. When I want to have a good, hard slug with a strong hitting partner or use my most powerful option for some singles, I'll use a C10. I'm now 51 and I probably love this racquet for giving me such a great combo of big gun performance along with superlative comfort. Most anything else through recent history has been some sort of compromise for me.
But I do agree that the C10 is a string sensitive racquet. Multifiber can play nice and soft, but this frame is already a cozy beast with its inherent "hoop flex". I have tried a multi in my C10's at least once or twice, but that string type usually softens at a steady rate after installation and eventually turns too soft for me before it breaks down.
I've also sampled a few poly hybrids in my C10's in recent years at various tensions, but the poly just plays too dead and clunky feeling for my taste. The hybrid that was easiest for me to relate to was Isospeed Baseline 1.20mm mains and Gosen OGSM crosses, both tensioned at 48 or 50 lbs. This light gauge of poly gave me better feel than most heavier gauges I tried and it seemed to offer a mild bump in the control department. The downside was that it seemed to turn the corner and go dead after only a few uses.
I love good ol' synthetic gut. I string at home and the reels I've been buying lately are Kirschbaum's standard (not premium) syn. gut in 16 and 17 gauge. Although the lighter gauge isn't quite so durable (no biggie for me), I love its feel and performance. I might switch to the heavier 16 ga. alternative in the middle of the summer heat, but otherwise I get everything I want (including moderate softness) with the 17 ga. syn. gut tensioned anywhere from 54 lbs. at this time of year up to 58 or 59 lbs. when it's warmer outside. Certainly not exotic stuff, but this string has been unbeatable for me.