You're overthinking this! 
There are Spyder Owners out there running 185 wide front tires in various low profile sizes under the stock fenders with no issues; others running 175/65R15 front tires with no issues; and very few who've had any problems fitting the same size & brand/model of the same tires you're planning on fitting! But do remember to check their pressures after they've been fitted - they AREN'T motorcycle tires, and despite needing about 40 psi for a moment or two in order to properly seat the bead, you'll only need about 18 psi in them to comfortably carry the weight of a fully (over)loaded Spyder.
Back to fitting them - the front fenders are flexible enough to allow even a 175/65R15 to be slipped in there, and the only things 'inside' the wheel well that have
any likely possibility of impeding that tire fitting are the screw heads holding the fenders on (which project into the wheel well about 10mm - if necessary, swap them for readily available pan-head screws); the struts supporting the fenders (which can easily be spaced out with a few washers
IF that's necessary, or gently pressured/bent a tiny touch so they clear everything); and possibly the wiring for the lights in the fenders (wiring which is sometimes run along the inside of the struts by a lazy assembler rather than tucked behind the struts where they should fit it!) There's nothing there that is insurmountable, and nothing that really causes any issues with fitting such a similarly sized tire to the OEM size!
So relax, and don't sweat the small stuff. Those tires will fit, even if there's some minor tweaking required - hey, as many Spyder Owners have found, some front tires with even
BIGGER 'nominal size labels' will fit in there too, often
without any minor tweaking, so you really don't need to stress about it.
Enjoy, and please tell us what you think of the new tires after you've done a couple of hundred miles on them. We really do like to hear how things went.
