Surround speakers slightly in front OK?

btw, where in the room is your seating position located?

what processor do you use? What exact speakers are you using? My initial thoughts tell me you have space over your door entry way, no?

Balance is always a key issue, with any properly setup system. In the case of the location of the speakers, in relation to imaging and steering of the soundfield, you might find it a little less than enveloping, ideally. However, it would not sound bad, all things considered, just as if most of the sound-field is happening in front of you. Think of it as a more extended front sound stage, perceptively, than what a 3 speaker set up would do.
A concern I would have in placing any speaker in a room, would be how each speaker actually sounds in a given location! This is the most overlooked of considerations in speaker positioning by novices. You can easily have speakers and seating positions located where there are "holes" and nasty peaks in the sound (of course, with today's EQ tech, this is of much less concern, as it can be rectified electronically), if phase issues between speakers. The former is more often a culprit.
I would say, as long as you're able to get good overall sound from these speaker locations, then you would be "OK". with it, if no other options.
With anything, there are usually compromises to be had, short of a perfect ideal, obviously. yes, I think you'll still enjoy your system if you need to leave them there.
Have you considered ceiling mounting some speakers? Is that an option?

Um, If I'm wrong, those speakers would work/aim much better set over your door way (I may be reaching here -life-style considerations, tastes, acceptable compromises, etc) in the "horizontal" position. Set vertically, you'll run into a bit of comb filtering from being up high, and you sitting down low. The water fall plot would be much better served for you up on the wall with those particular "Dappolito" configured speakers. Its' a thought. In fact, if I had to use those speakers as rears, unless I could get them down lower (actually, that compromises localization and image height a bit), I would be setting those rears in a horizontal position above or slightly behind my seating location, tilted a bit down towards the listeners, yes! Why? Again, the propagation of the sound will steer or spread across the seating area better, in your setup. The other way around, and you'll be rolling the highs off somewhat, and combing the mid-range, somewhat. That is a fact, btw. I used to deal in those speakers, installed them, and have owned the TSS-750's in the past.
Actually, another consideration is to use the smaller otherwise excellent little TSS-750's as rears instead! They are still very little dynamic speakers, they will work better in terms of proper sound distribution, set up different ways, they're much smaller (and thus more flexible to position), and they use the same exact drivers and crossover as the TSS-750's! With your setup and system, that''s what I'd chose to do, if you couldn't deal with the rears properly. And sounds like you can't.
You can find the TSS-750's around dirt cheap if you look. Somwhere in the $30 ea neighborhood (were $99). Again, it's a consideration for you.
Yes, for the record, if I had to use your TSS-1100's as rears, I'd be turning em horizontally, and putting them just above my door, sandwiched between the ceiling, tilted slightly down - same for the back. If you put em on the back wall, imaging and tonality will be a major challenge, and you won't get such good sound from the speaker(in short, the sound will be very very roll-ed off in the high's/upper mid's).
Well, anyway, I gave you some thoughts to consider, for what I believe would possibly maximize your performance, and possibly be workable ergonomically. Yes, if it where me, I'd be ditching the 1100's for the 750's (same frequency response range, same clean sound, more open sounding, and actually just as dynamic, basically - yet much more flexible, and they'll disapear into the room better, visually).
Good luck