You're correct, rarely do we see any final designs with perfectly ideal beta-strands. Solutions from this puzzle would need some refining before testing (perhaps in a follow-up puzzle?). Still, we wanted to mix it up a little in the design category, and this format presents a simple yet interesting challenge. We have some ideas for future puzzles that might be less restrictive.
Unfortunately, in the current client there is not a good way to put a "flexible lock" on one region of secondary structure. I agree, that would have been a more realistic challenge.
I like to use all types of SS for designing puzzles, but understand that scoring system favors helices. I'm not sure a follow-up would help unless there were some way to insure use of at least one strand.
It may be a silly question, as I don't understand the particulars of how bonuses or filters work, but can't there be a bonus or filter for having at least one strand of length "x" that would tip the helix bias?
Unless you can exclude the fixed segs the rebuliders choke, also idealising has to be done in a minimum of two sections. I am ok with having a sheet segment, just saying.
I'm guessing that by "choke" you mean they have no effect on the locked segments? None of the rebuild scripts I've used have abnormally ended. It's possible that the scripts I use exclude the locked segments, but I haven't checked.
In my original comment I had info about idealization issues, but removed it before posting. I extended the locked sheet by two segments in my design. I could click Idealize for each of the two additional segments, but couldn't use "Ideal SS" on them because it yields the message "Segment is locked". The result is a funky looking strand since the two segments bend, the locked ones don't and are perfectly straight.
Granted, in the design stage perfectly straight strands are desirable but it's expected that they relax as the puzzle develops. Isn't there a way to lock the type of SS structure but keep its flexibility? Or is the inflexibility intentional?
If it is intentional, could you give us some insight as to why? Understanding why might help us to narrow our focus and come up with better solutions.