For what it's worth, here's another vote for keeping the 175. I'm the same size as you, and would honestly be shocked if more than 1 or 2 posters on here ski faster or more aggressively than me. former racer, blah blah. I bought the 88 in a 175 about a month ago.
In fairness, I haven't skied these yet, so my opinion is only based upon everything I've read and heard, but it pains me to see you getting doubts due to what is mostly muscle flexing from others, in my opinion.
You get a lot of people skiing on bigger skis than they NEED to, purely for ego. Do you think that Glen Plake uses downhill boards on gunbarrel because they are the best ski for the job? Sure, he can handle them... but why does he really ski on them?
I am an absolute research nut, and spent so much time looking into replacing my recently deceased 178 g4s that it's sickening. I have zero tolerance for skis not performing at wicked fast speeds. Here is what I found...
Across the board, from many, many sources, the head 88 in a 175 has no speed limit! It is regarded as being as stable and damp as a GS race ski at high speed. It is much more forgiving, yes, but that is due to it's construction reacting differently at slow speed vs. high speed. And I'm sure it has less energy out of the turn and isn't as quick edge to edge. Of course you could ski the 186, and of course you would have no problem handling it. If you have a serious race background at 24, you probably grew up racing on 210 rc4 planks!
The thing is, what do you gain from skiing the 186? Pretty sure you'd only gain float, but come on now, we're talking about a ski with a 89 mm waist here! You weight 165 lbs! The 186 is for folks who put no value on added flexibility in the trees, bumps, etc., or for those well over 200 lbs who can use a little extra float, or, as is fairly obvious from some of these posters, those who get a kick out of telling people online that they ski the longest length, and that anything else is less than badass. Remember that ski manufacturers are well aware that these people exist, and make ski lengths accordingly to fill the market. I'm sure you'd be able to take the 186 in the trees and bumps "no problem", but I'd bet you'd be working a fair amount harder at it, and would have nothing to gain from it but weary legs by 2pm on a powder day and feeling like glen plake without the mohawk (presumably).
Keep the 175, ski wicked fast all over the mountain, get more than enough float and crud busting capability, and enjoy better maneuverability in the trees, bumps, and at slow speeds.