Difficult Tiling Puzzle with a Hint

Here is a difficult tiling puzzle; a version of the puzzles in thing:5268401 "Ten Tiling Puzzles". In this puzzle the pieces are all different which makes the puzzle difficult to solve by trial and error. It can be done but the solver needs persistence.

The puzzle is composed of 8 pieces; 7 hexominos and a single heptomino. No two pieces are the same. As in thing:5268401 the target is a square box which represents a 7x7 array of 49 squares.

The pieces are given as two stl files each of which contains 4 pieces. Set a contains hexominos 24, 26, 29, and 30 and set b contains 3 hexominos and a heptomino - hexominos 21, 22, 23 and heptomino 33. If printed in the same color the puzzle is difficult, if set a and set b are printed in different colors a hint can be given - see below.


A target container is also provided. It is not really necessary if it is understood that the pieces assemble into a square. However it eases the solution serving as a container for partial work a