I'm not familiar with any "stop" on the new idler pulleys either. There are some minor differences in the idler hub area to accommodate the new roller bearings, but operationally it functions like the earlier ones. In some applications it is possible for the GT drums to contact the GT idler pulley near the full forward drum rotation, but it is not intended to be a limiting device. If you order a new idler for your older drive it is doubtful that you would get the same result.
For $7 you can always try it -- worse case, you would have upgraded your idler to roller bearings.
BTW, the front cockpit on your 2013 Oasis is slightly longer than the rear cockpit (unlike previous versions). Your tall neighbor will find more leg extension space there before hitting the limits of the Drive. As you know, your TI had even longer cockpits, rendering the issue moot for most users. Having both tandems, you can always accommodate your neighbor more comfortably in the TI (kayak mode).
