This is what a few photos and posts on page 8 of 10 pages of discussion on wants and desires.
This is what the 'upselling' of Utopia aftermarket Rider's backrests look like fitted with the Gel Rider Solo and Gel Pillion (actually in this photo they have a std early 'bread loaf' narrow pillion with the accessory Gel Rider Solo that you have, the Utopia is large but folds forward for mounting unless you like practising a ballet pirouette.
Your Utopia attaches to the pillion mount bracket without interference as seen above or 3rd photo. The 2nd photo gives a close up view of the same backrest with a different lower mount to be inserted inside the Dual Triumph Classic and R3Touring Dual seats by owner surgery. They are very good too but much easier to mount your Solo seat version with ANY Solo Rider's seat and I use one with a custom Russell Daylong Riders Solo and/or stock Riders Solo seats as used since 2010 on with a wider rear pillion as stock and earlier from 2004 with the 'Bread Loaf' pillion on Standard R3s