The Leclerc Fanny has quite a large sweet spot – that is, the area where mechanically everything works at optimum performance in terms of the shed opening and the weft being beaten in.
In this photo the fell (the last weft pick) is approximately half way between the breast beam and the reed. It may come as a surprise to some people that, imho, it is now time to advance the warp.
The temptation to keep weaving needs to be overcome because from this point on the shed geometry will begin to change in ways that are going to adversely affect the quality of cloth.
The warp will have to open at a greater angle putting increasing strain on the threads. If weaving continues much beyond this point, the weft will not seat properly around the selvedge threads and loops can develop which may not become apparent until the fell is moved forward towards the breast beam. The angle of attack of the beater will change and the weft may beat in differently. If the weaving continues even further, the shed will reduce to the point where the shuttle may not fit easily through the shed. A tender warp will be under too much strain and the additional abrasion of the shuttle may damage the warp.
This photo is immediately after advancing. The fell is about two inches from the inside of the breast beam.
It is much better to stop and advance more frequently than to try and force the loom to work beyond its mechanical ability. Truly a case where stopping more frequently will get better results faster.