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Hallo Hanno.

What an interesting question. 

I've been a Bygrave and Fuller lunatic for years, having built homemade replicas of the Fuller 2 (with sines) and a mini version (more later) + a Bygrave. Actually had no trouble building accurate replicas with vitually no skills, so not sure where others found the problems. (can give build details)

I have used both Fuller 2 and Bygrave to do numerous LOPs. Using the Fuller in conventional mode with the other Fuller scale etc,it takes twice as long as the Bygrave, which also, incidentitally gives Azimuth.( You have to do same work again with Fuller to get the Az)

The Fuller is great for everything like lunar clearance and any calculations normally now done with a calculator. I get 4-5 decimal place accuracy versus calculator.

However, you seem to be suggesting a simple slide  rule using just the log sine scale (Eg on Fuller 2 inner tube) or log cos scale (eg Bygrave outer tube) + 2-3 cursers (transparent tubes with curser lines? and no need for the Fuller slide rule mutliplication/division scale?)

Well, I'm no mathematician , so missed that. 

Please give me details of what the simple slide  rule looks like, maybe pictures (I'm simple minded!) .I have plenty of prototype Fullers and Bygraves to quickly adapt, if you show me the way with the cursers and explain to a innumerate enthusiast what moves/sets need to be done to get the answer.

i can test this within days (pending surgery depending!).

look forward to hearing from you asap. Can send word docs re my work on request.

Best wishes 

Francis