Here is my take on converting 1/76th Plastic kits to 18/20mm scifi.
I got JB models 1/76th Saladin & 2 Saracens kits .
I my opinion these are small when compared to 18mm minis , though they are good for pure 15mm. I decided to make them bigger by sawing them in half & inserting plasticard strips. I also used card & sprue for the build. It does take serious thinking & measurements to get the pieces the right size but it is do able not impossible.
I realised that the original wheels are small so I decided to use larger ones .I had to use plastic sprues as axles.
The Apc's would looked good as Imperial Guard Taurox.
They do look nice packed with riding infantry. The problem would be whether to glue them or not & use blue tack.
Thanks for your comments. Z