| Game |
| Result | Moves |
Year | Event/Locale | Opening |
| 26. S Polgar vs M Sion Castro |
| ½-½ | 22 | 1989 | Leon | C15 French, Winawer |
| 27. S Estremera Panos vs M Sion Castro |
| ½-½ | 19 | 1989 | Leon | D24 Queen's Gambit Accepted |
| 28. M Sion Castro vs J Campos Moreno |
| ½-½ | 22 | 1989 | Leon | E06 Catalan, Closed, 5.Nf3 |
| 29. M Illescas vs M Sion Castro |
| 1-0 | 42 | 1989 | Leon | A15 English |
| 30. M Sion Castro vs F Sanz Alonso |
| ½-½ | 17 | 1989 | Leon | C92 Ruy Lopez, Closed |
| 31. M Sion Castro vs A Romero Holmes |
| ½-½ | 45 | 1989 | Leon | B78 Sicilian, Dragon, Yugoslav Attack, 10.castle long |
| 32. J Pinter vs M Sion Castro |
| 1-0 | 32 | 1989 | Leon | D83 Grunfeld, Grunfeld Gambit |
| 33. M Sion Castro vs Z Franco Ocampos |
| 0-1 | 39 | 1989 | Leon | B56 Sicilian |
| 34. M Sion Castro vs Chiburdanidze |
| 0-1 | 40 | 1990 | Salamanca | C97 Ruy Lopez, Closed, Chigorin |
| 35. J Ochoa vs M Sion Castro |
| ½-½ | 13 | 1990 | Leon | B40 Sicilian |
| 36. M Illescas vs M Sion Castro |
 | 1-0 | 40 | 1990 | Leon | E94 King's Indian, Orthodox |
| 37. M Sion Castro vs Granda Zuniga |
| 0-1 | 62 | 1990 | Leon | B06 Robatsch |
| 38. M Sion Castro vs C Garcia Palermo |
| ½-½ | 12 | 1990 | Leon | C42 Petrov Defense |
| 39. J Magem Badals vs M Sion Castro |
| 1-0 | 24 | 1990 | Leon | A36 English |
| 40. M Sion Castro vs F Sanz Alonso |
| 0-1 | 33 | 1990 | Leon | C61 Ruy Lopez, Bird's Defense |
| 41. A Romero Holmes vs M Sion Castro |
| 0-1 | 41 | 1990 | Leon | B40 Sicilian |
| 42. M Sion Castro vs Z Franco Ocampos |
| ½-½ | 24 | 1990 | Leon | B58 Sicilian |
| 43. M Sion Castro vs L Bass |
| ½-½ | 13 | 1990 | Leon | B78 Sicilian, Dragon, Yugoslav Attack, 10.castle long |
| 44. F Braga vs M Sion Castro |
| 1-0 | 28 | 1990 | Leon | D37 Queen's Gambit Declined |
| 45. M Sion Castro vs A I Hamed |
| 0-1 | 41 | 1990 | Novi Sad Olympiad | B06 Robatsch |
| 46. M Sion Castro vs T Thomsen |
| ½-½ | 20 | 1990 | Novi Sad Olympiad | C11 French |
| 47. S Sarno vs M Sion Castro |
| 1-0 | 35 | 1990 | Novi Sad Olympiad | D97 Grunfeld, Russian |
| 48. P Cramling vs M Sion Castro |
| 1-0 | 32 | 1991 | ESP-chT | D86 Grunfeld, Exchange |
| 49. G Milos vs M Sion Castro |
| 0-1 | 21 | 1991 | Pamplona op | A25 English |
| 50. H Urday vs M Sion Castro |
| 1-0 | 66 | 1991 | Palma de Mallorca Open | A15 English |
Kibitzing
