Most everyone I know has the regular leg & belly straps. I criss-cross the straps both under the belly and between the legs to take up excess slack (not tight just enough so a hoof can't get through). I see a lot of horses standing out in pastures with those straps hanging so low under them and keep thinking that they're accidents just waiting to happen.
How cold is cold? You may only need a mid-weight water proof turn out blanket. Buy 1200 denier over 600, its worth the extra money - they're more durable.
Up in here in the Northeast, the only time we've had G in a mid weight blanket was a few nights where the temps dropped into the 20's. There are a few horses at my barn that are already wearing their winter blankets and the temps are back into 40's at night and 50's (yesterday 60's) during the day. I keep thinking what's going to happen when the temperature drops into the teens and single digits? Hopefully, the owners will start bringing them in.
How they explained it to me was once you start blanketing a horse, they no longer have the ability to keep themselves warm

Now I could understand if the horse has been wearing a blanket night and day for weeks at a time, but after a week?? 'splain please?? G's hair still fluffs up and he is getting fuzzier by the day.