Hi wce
Christmas Day was okay, but Santa needs
to lift his game post Covid - whenever that is ...

I do not believe anyone can answer your question, but I am
impressed that you have factored in engine weight.

I was not aware that modern replacements are kilos heavier! shocked

The general consensus is that the gauge steel on the 45 was
marginal, with fatigue cracks appearing after the expected life
of the chassis. Hardly a design fault (in my view).

I do not know whether weight or vibration caused some failures.

Maybe a member has another view.
Nonetheless, I'm glad you have asked the question.

Cheers
----------------------
Jack