Strap-onless strap-ons

A starp-on harness is a good initial investment because it can be used with a variety of toys including strapless ones (if desired).
The strapless ones seem to be pretty good, though depending on who you talk to. The Share line and the feeldoe line seem to get good marks from most and present the best chance that they can be used completely without a harness. The Nexus line would probably be somewhat more difficult for the giver to hold inside without a harness. I think the harness option might be better for versatility, but the Share might represent an excellent choice for you and your girlfriend as well.

Personally, I would say no... just because they're harder to navigate. Certainly possible, and you can add a harness to get more stability while keeping the internal stimulation. There are also some harnesses that will hold a cock inside the wearer as well, so you have more options.
I'd agree with Jimbo that either the Share or Feeldoe is your best bet for doubles like this, the Nexus just doesn't cut it.

While I have not used the share, I do have some experience with the Feeldoe Slim and a double strap style harness. It is certainly possible to hold the Feeldoe in and have pretty good control over it, IF the wearer has pretty good vaginal muscles. You can use a harness with the Feeldoe and the Share, and my experience says that the Feeldoe works pretty well with a harness, only you don't have as much control over the angle of the dildo because of it being stuck in the harness.

A harness and strap on dildos would lend a pretty good threshold of variety as you have a lot more options available than you do when buying a double ended dildo. Also if dual stimulation is important (strap on sex is always stimulating though ) I might suggest a harness that allows for two dildos to be used in it, one facing outward to penetrate the partner, one facing inward to penetrate the wearer. Outlaw leather makes some good harnesses for this, just be warned they are expensive.

I use my Feeldoe for Pegging with my husband, and purchased that particular one because of the firmer silicone and the included vibrating bullet. Looking back on it, I wish I had purchased the Syd harness and two dildos instead (or maybe in addition), as we found the Feeldoe Slim to be rather short. Don't get me wrong, we really love it. The shortness of it just makes some positions more difficult and it lends to a pretty shallow penetration. The Feeldoe More is an inch longer, and I am yearning to give that hot red beast a try

Best of luck, and hope you find something perfect for you and your girlfriend!

My wife Di and I started with the Feeldoe slim and as long as she lays on her back and I ride on top of it it's fine, but even though she has super strong Kegels she has trouble controlling it in any other position.

We recently bought a Nexus Sr. dildo and a two strap harness and it's great. With either the Nexus or the Feeldoe in the harness Di is in total control and can thrust and pound away on me as much as she wants.

Without the harness Di got nothing at all from her end of the Feeldoe. When she puts it in the harness or uses the Nexus she has as much fun as I do and usually cums along with me.

I'd say that a harness is the only way to go, more control and you don't spend time worrying if it's going to slip out or not.

Good luck and have fun sexploring.

I still have to practice a lot to handle it as a giver, however, as a receiver this is something phenomenal.
First time when I "put it on" I had a look in the mirror, just for the sake of imagining how men feel when they are erected and somehow I started thinking about having a penis instead a vagina is a better idea. Weird.

The Share and Feeldoe both work well for us. They give my wife some excellent stimulation compared to just a basic strapon. If she really wants to get wild she'll use a harness with the Share. These two product lines are pretty versatile so you can't really go wrong!