Is it possible to partially update IFO tables?

[iomagic]

I'm trying to copy a Benny Hill DVD, and it has 13 PGCs; first 3 are the relevant stuff, then go 0-length PGCs and PGCs referring to the programs already present within PGC1-3 - they are called from different menus. Well... if I extract these cells again, I increase the size of final DVD, duplicating existing material, and I'll have to decrease the bitrate and lose quality. If I don't, then what to do here? Just create blank PGC with few black frames, and then use IFOUpdate to fix the tables? But if I touch the original IFO, all the time tables will get overwritten with the new data, so the original navigation will be lost! Or it is a hopeless case and I'll have to manually create these PGCs in Scenarist by pointing to the cells within other PGCs (just like the original does it) and then only update VTS sectors? I'm really at a loss here, and honestly I don't have a firm grasp on the empty PGC copy methods. Attached is the IFO which should clarify all the nonsense I wrote here :)

Thanks, hope the gurus have the answer! (And I hope the answer will be more than just a couple sentenses long, and it would actually have an explanation of what to do)