I started a similar thread about a month ago when we needed to purchase a new bike and I wanted a platform as my hanging one seemed to be killing my mixte. We were concerned with both a mixte and fenders. The 1up was highly recommended to me and confirmed that it was fine with fenders Here's the comment re that sent to me off-list "I have fenders on my Surly Long Haul Trucker and I bought
the foam pad thingy 1Up makes for a few extra dollars which
works very well and doesn’t crush the fender. I did notice
that on the back fender that the struts (the arms that
straddle the wheel) actually touch the fender struts which
connect it to the back stays - at first I was a bit worried
about bending them & then I realized that if anything, it
kept the bike more securely upright in the rack, without me
needing to “clamp” the fender/wheel as hard, and that it had
no ill effects on the fender alignment."
I really liked everything I saw about the 1up, but we ended up going with the Hollywood Rack instead (also recommended in the thread). It was about half the cost and seemed fine, even if not quite as substantial. The initial install was pretty easy - you have to set the platforms in the proper positions for the specific bikes and that takes a couple of minutes. For $350 we got the carrier that works either as a 2-bike carrier or adds the extension to make it a 4-bike. To this point we've only used it for the 2 and haven't even attached the extension. It loads so fast it is amazing. As a non-tall woman I love that I can easily lift my bike on/off and that it puts things at eye level.
The bar is nicely padded and clamps on the top tube of the bike and on my mixte it nestles perfectly where it meats the seat tube. The instructions are to place the bikes opposite one another but when we did that, there was some slight interference and we put them the same direction instead of messing with seats, etc. And it worked perfectly. Both are very secure. It is a little concerning that the tires extend through the platform so I have visions of crunching my bike if the tires hit on an incline. But it is very clear that the bottom of the carrier will hit first since the platforms sit up higher, so I know they are safe. We are able to keep the rack on all the time and tilt it for access to the back of the car, not quite as nice as the swing-away hanging rack we had before, but not bad. And it is so easy to unload/load the bikes that even if we have to remove them to do something (like pull a kayak off roof), it's not a big deal.
We tow our jeep behind an rv with the rack mounted to the jeep. The instructions say not to use it for a tow vehicle or on a trailer, but it seems to be just fine and it seems like a standard thing with all the racks and we've always done it w/o problems. So just hoping it is just a standard disclaimer which must be related to the added length affecting how it handles on an incline but we have to be careful of that already (the hitch between the rv and car would likely hit so we'd be forewarned)
Here's a picture attached) of our 2 bikes on it the first time we used it. Not sure it's the greatest picture but could take better on Mon/Tues when we load up for our big trip. We will also probably be putting the added attachment on at that time so we have the flexibility to carry other bikes with us since it's a group trip.
(We had also considered the Kuat since it seemed great, but never had an opportunity to see one and it was very pricey also. Saw one week before last in a parking lot and it is a beautiful, sturdy-looking frame. Looks much more substantial than ours, but we are completely happy with our purchase)