I can only speak about the 5 wt Loomis imx-pro short spey (never thrown the 4 wt). As some have mentioned above, the 5 wt is a strong rod....But definitely not a broomstick-like one. By this, i mean it is what i would rate as more of a small steelhead, large trout (20+ inches) rod. The grain window for skagit heads is 350-390 gr. The 5 wt easily handles sink tips of 80-100 grains also.
The action requires what i would say is a more easy, controlled stroke. If you tend to more power on your forward cast, this may not be the rod for you. With that said, once you get the action dialed in, casts over 80 ft are the norm if you need distance.
At 11’11”, i have not had good experience with the shorter skagit heads ( 16-17’ airflo scout or 17’ rio
skagit trout) that the gear reviews recommend for these 4 and 5 wt rods. The 20’ skagit heads (rio skagit short or SA freightliner) work more better....at least for me.
As for casting into the wind, it has performed very well. It will throw a tight loop close to the water with a sidearm cast.