Hi Fastsky long time no see. Cool to see you are doing some multi stuff.

The manufacturered plastic type wing hold downs are fine in themselves, the theoretical weakpoints should of course be the nylon bolts but another posible weakpoint with those could be the screws into whatever structure you attach them to. This in much the same way that the threaded (or 'T' nutted plywood fuselage cross plate often has a weak point where it is epoxied to the fuselage sides.

The real bottom line is either system could work just fine and either can be compromised with poor workmanship so it is really up to you.

Now just another point and it is a hard fact that no one considers. This wing to fuselage joint in a multi engine airplane where the engines are wing mounted actually receives less stress than a conventional single engine airplane of a similar size and weight. The greatest percentage of aircrafts total weight is already in the wing and not transferred throught this fuselage to wing joint. This I pointed out to allow you to be a bit more comfortable and it does not of course to mean you can be lax with the building practices.

Perfect illustrations of this are my Quad Kaydets, 12.5 pounds or 15.5 on floats virtually all this weight is in or on the wing with the fuselage being even lighter than the the stock ARF Kaydet fuselage. Even more extreme example of this is my Six Pack Telemaster.

Just some food for thought, Cool twin

John