Short answer - don't.
Now this is how the Steagle sat on my shelf for nearly a year, which was long enough for the top rear panel to almost nearly not quite fit where it needed to be...Seriously, it was, and still is way out from where it ludicrously claims it ought to physically be able to exist. The fit is so bad, I eventually had to pin both sides of the fuselage to the floor, even after hours of heating and filing. Even then, the front ramp sits in a gap that is too big for it, requiring plasticard and Greenstuff to help out.
I had to remove significant amounts of the rears of the top wing parts (where the Greenstuff is in the above pic) just to get them in, the main issue being that the front plastic top panel just wouldn't sit in the right position, consequently shifting all the parts behind it out of position...The engines are pinned into the hull for strength, most of the weight is on the wings and rear of the model (which also causes 'issues' in terms of flying stand stability). Don't forget to pin the landing skids to their legs either, I didn't trust them to hold the weight of the thing alone. Magnetising is an option here.
Here she is, pretty much done and awaiting undercoat. What a labour of...well, it wasn't love, certainly. Bit of a grind, really!
Here you can see the WIP 'Greenstuff covered in Liquid Greenstuff' phase of the project. Yeah. It looks better than this now, promise!
Overall, this is a great looking model (remember the brick-like abomination this kit is based on) that is dragged down by horrendous warping and bad fit. Equally it's so rear-heavy extra attention will be required to get it to go safely (and/or semi-permanently) on its flying stand. God-Emperor knows how I'll transport it either. I can't really recommend the kit itself to anyone, never mind the inexperienced modeller, just get a Spartan instead. (Der H: Funny you should mention that...) It does pretty much the same job and is more survivable (on and off the battlefield). However, if you really want, or list restrictions require you to have a flyer transport, you don't have any other option in this price range...in that case, Emperor be with you.