Harbeth owners and fans

I am considering Harbeth speakers for my LR remodel. Their placement needs to be in openings/built in bookcases on each side of a fireplace. The areas are large enough to allow several inches space on each side and top of speakers and a foot or more behind them. If I place the front of the speaker even with the front of the opening will it penalize the performance potential of these speakers?
Almost certainly. The only way to see how much of an effect it will have is to try them. Also, any speaker will be effected, not just Harbeth. Most bookshelf speakers are meant to be put on stands and not bookshelves.
In your favor, however, the ported Harbeth models (the P3ESR is sealed) have their ports on the front.
Thanks for response. I am thinking compact 7 or shl5. I thought the forward facing port would make the area around and behind a non issue. This is a big room, most use being family tv but audio jewelry is always good in any room. Thx again for feedback and anyone else please chime in with any thoughts.
The SHL5s actually put out a lot of bass/mid-bass (I have not heard the 7's, but probably similar in this regard). I would be concerned that these speakers would get very boomy inside another enclosure, and even moreso than others since they are designed to have a 'breathing cabinet'. You could only be sure by trying them out, of course. If it were me I would think about a small but heavy cabinet speaker (like those made from stone or corian) with limited bass for the bookshelfs and a subwoofer somewhere else in the room. If you like the fantastic sound of the Harbeths though, perhaps the P3's slightly elevated off the shelf and an added subwoofer would get you there. Another factor is the room - if this is a large room, and you are sitting more than 8' from the speakers, I believe my advice above would apply even moreso the farther away you got from the fireplace from there. The Harbeth's are great at nearfield listening, but the farther you get away you may lose some of that magic and get lost in the boominess provided by the bookshelf/enclosure if you went with the larger models.
I should have added, I am not advocating only speakers made from stone cabinets, just making the point that the heavier/thinker/denser the the better, in general, with the stone being the extreme case in that category. There are many speakers with 1"+ MDF that would begin to fit in this category.
Thanks Jimmy,
The issue you addressed above describes perfectly what I had prior to the remodel. I have used Infinity Reference Standards and Definitive Tech's in these wells through the years, both are rear and/or side firing, and the sound was terrible. It is kind of a strange application, the wells/openings are inset into the main front wall and the bottom of the opening is 18" off the floor. So, I thought a larger,forward firing only, bookshelf might be the perfect ap to get the tweeters @ 38-42". We will also be 10'-20' from this wall so I definitely need to rethink this. Any brand suggestions to explore? What is your opinion of some nice flush mount speakers? Wisdom, etc. ?
Thanks again.