i think you'll find that if you stick to an approproate tyre, 205/40/17 to 225/40/17 you'll very likely get away with it, and on an 8" wheel rim they will be fine
TwinCam i think the reason you have/suspect clearance issues is that you are over-tyred for a 7" width rim,
in my own humble opinion of course, i'm not a tyre fitter, just a wheel whoar!
i have run 19's with a similar offset on a lowered 156 before, without rolled arches, and only had to contend with a little area of inteference from the plastic inner arch in the front which was easily dealt with.
lovely wheel the Toora 560, one of my favourite brands of old is Toora, usually lovely quality, and that design is a nice inbetween alternative to the similar OZ offerings, but they are also very nice in SuperTurismo and SuperLeggera.
and one final note on the Toora's, is that the bolt holes are often quite narrow, but on an et35 be quite visible too, so you may find the Tuner Bolt versions of 2mm wobble bolts will both fit and look better in an aftermarket wheel of that type, and they are only about £10/£15 dearer than a full set of normal bolt head wobblers,
thats what i'd do mate
all the best, good luck, and don't forget a piccie when you're done!