There are a few differences,mostly engine starting procedures and the fact that there is a prop sponning next to you.and some are staggered.on my b-24 the inner engines are in front of the rear engines.start each one set it and kill it,refuel all of them then I start the iutside engines first then the inners.when you loose an engine not much happens other than the plane slows down a bit.luckily I have not lost 2 on the same side .I used a dubro kwik clip for the glow plug connection so I could stay away from props.in most cases 4 engine planes are scale and are heavier and have a higher wing loading than what you are flying now we are talking over 30 oz/sq ft closer to 40 oz/sq ft.because they are scale they are more complex and cost more.If you want a multi engined sport model for four .25 get a 90-120 size plane like a sportster or 4* and add 4 nacelles and point the nose.should fly easier than a scale ship.right know fly the twinstar and see what happens when you loose an engine,then see if you weant to continue.You say you have 3 .25.how about a tri motor,rcm plans has a ju-52s that is foe 3 .20 size engines and would not be difficult to build.