remember that the Willcox & Gibbs is a chainstitcher not a lockstitcher. It is usually assumed to be for decorative stitching, but the research I have read indicates that the specific type of chainstitch done by the W&G is a "twisted chainstitch" which is supposed to hold better than a traditional lockstitch.
I have not had time to test it out myself yet
P.S. As a dad of three daughters I LOVE the fact that you are doing tiling with your dad. All three of my daughters are "girly" but still up for "sweaty work". My middle daughter and I are in the middle of rebuilding the engine on her 1990 Jeep Cherokee this week and next. My youngest does almost ALL of her own car repairs (and jewelry, and sewing, and...) in fact she redid the oil pan on HER Jeep last weekend.
[ATTACH=CONFIG]401562[/ATTACH]