hi jean
always nice to have your input .with all respect to both yourself and mrs. merkelt she could be wrong or half right anyway .
it would seem possible :
1. that mr. merkelt drew up a design in , let us say 1946 for arguments sake , he did as far as we know nothing with this design .
2. possibly by 1956 or so mr. m was thinking that fibreglass was more feasible than an aluminium / ash frame design
3. he would have been aware of bruetsches designs - they were well publicised - this bruetsch was better at than producing cars
4. he may have even met egon bruetsch when he toured britain in 1954or 55 ( anyhow at least a year or so before the later bruetsch designs were shown oct 1956 motorcycle show at earls court )
all the above is POSSIBLE it seems and , i have said with respect , it is just possible that mrs. merkelt may have not KNOWN the facts but did not like her husband accused of plagiarism or suchlike